Develop Reference

My Activity comes out as a Blank even though it shouldn't?

I'm a complete beginner with coding and decided to try out android studios for fun without having formal training or lessons for the basics so I'm sorry if this seems like a dumb problem but whenever I try to run my code it just comes off as blank? Any idea how to solve this?
Here's a screenshot of what comes up
package com.example.trtalpha17;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.Toast;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import org.jetbrains.annotations.NotNull;
public class Register_Tutor extends AppCompatActivity {
private static final String[] SCHOOLS = new String[]{
"A", "B", "C"
};
private static final String[] COURSE = new String[]{
"Bachelor of Science in Social Work (BS Social Work)",
"Bachelor of Science in Marine Transportation (BSMT)",
"Bachelor of Science in Food Technology (BS Food Tech)",
"Bachelor of Science in Nutrition and Dietetics (BS Nutrition and Dietetics)"
};
private static final String[] EDUCA = new String[]{
"Grade 9", "Grade 10", "Grade 11", "Grade 12", "1st Year College", "2nd Year College", "3rd Year College", "4th Year College", "5th Year College", "Graduate"
};
private static final String[] TITLES = new String[]{
"Mr.", "Ms.", "Mrs.", "Mx."
};
EditText metEmail, metPhone, metPassword, metPasswordconfirm, metNamefirst, metNamelast;
Button mbutton;
ProgressBar progressBar2;
FirebaseAuth fAuth;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register_tutor2);
final AutoCompleteTextView metTitle = (AutoCompleteTextView)findViewById(R.id.etTitle);
final AutoCompleteTextView mautoCompleteTextView = (AutoCompleteTextView) findViewById(R.id.autoCompleteTextView);
final AutoCompleteTextView meduc = (AutoCompleteTextView) findViewById(R.id.educ);
final AutoCompleteTextView metcourse = (AutoCompleteTextView) findViewById(R.id.etcourse);
metTitle.setThreshold(2);
mautoCompleteTextView.setThreshold(1);
meduc.setThreshold(1);
metcourse.setThreshold(1);
ImageView marrow = (ImageView) findViewById(R.id.arrow);
ArrayAdapter<String> adapterarrow = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, TITLES);
metTitle.setAdapter(adapterarrow);
ArrayAdapter<String> adapterschools = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, SCHOOLS);
mautoCompleteTextView.setAdapter(adapterschools);
ArrayAdapter<String> adapteredu = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, EDUCA);
meduc.setAdapter(adapteredu);
ArrayAdapter<String> adaptercourse = new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, COURSE);
metcourse.setAdapter(adaptercourse);
marrow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
metTitle.showDropDown();
}
});
metNamefirst = findViewById(R.id.etNamefirst);
metNamelast = findViewById(R.id.etNamelast);
metEmail = findViewById(R.id.etEmail);
metPhone =findViewById(R.id.etPhone);
metPassword = findViewById(R.id.etPassword);
metPasswordconfirm =findViewById(R.id.etPasswordconfirm);
mbutton = findViewById(R.id.button);
progressBar2 = findViewById(R.id.progressBar2);
fAuth = FirebaseAuth.getInstance();
if(fAuth.getCurrentUser() != null){
startActivity(new Intent(getApplicationContext(),MainActivity.class));
finish();
}
mbutton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String email = metEmail.getText().toString().trim();
String password = metPassword.getText().toString().trim();
if(TextUtils.isEmpty(email)){
metEmail.setError("Email is required.");
return;
}
if(TextUtils.isEmpty(password)){
metPassword.setError("Password is required.");
return;
}
if(password.length()<6){
metPassword.setError("Password length must be at least 6 characters.");
return;
}
fAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull #NotNull Task<AuthResult> task) {
if(task.isSuccessful()){
Toast.makeText(Register_Tutor.this, "Registration complete.", Toast.LENGTH_SHORT).show();
startActivity(new Intent(getApplicationContext(),MainActivity.class));
}else {
Toast.makeText(Register_Tutor.this, "There was an error making your that request. Please try again later." + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}
}
});
}
});
}
}
LAYOUT
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".Register_Tutor">
<TextView
android:id="#+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="40dp"
android:fontFamily="cursive"
android:text="Register as a Tutor"
android:textColor="#000000"
android:textSize="28sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.497"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TableRow
android:id="#+id/tableRow"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/textView2">
<AutoCompleteTextView
android:id="#+id/etTitle"
android:layout_width="68dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:drawableLeft="#drawable/ic_baseline_person_24"
android:drawablePadding="5dp"
android:hint="Title"
android:inputType="textPersonName" />
<ImageView
android:id="#+id/arrow"
android:layout_width="16dp"
android:layout_height="45dp"
android:layout_marginStart="4dp"
android:layout_marginLeft="4dp"
android:drawablePadding="5dp"
android:src="#mipmap/outline_arrow_drop_down_black_18" />
<EditText
android:id="#+id/etNamefirst"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:hint="First name"
android:inputType="textPersonName" />
<EditText
android:id="#+id/etNamelast"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:hint="Last name"
android:inputType="textPersonName" />
</TableRow>
<LinearLayout
android:id="#+id/linear1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintTop_toBottomOf="#+id/tableRow">
<EditText
android:id="#+id/etEmail"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:drawableLeft="#drawable/ic_baseline_email_24"
android:drawablePadding="5dp"
android:hint="Email address"
android:inputType="textEmailAddress" />
<EditText
android:id="#+id/etPhone"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:drawableLeft="#drawable/ic_baseline_local_phone_24"
android:drawablePadding="5dp"
android:hint="Phone number"
android:inputType="phone" />
</LinearLayout>
<LinearLayout
android:id="#+id/linear2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/linear1">
<AutoCompleteTextView
android:id="#+id/autoCompleteTextView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:completionThreshold="1"
android:drawableLeft="#drawable/ic_baseline_school_24"
android:drawablePadding="5dp"
android:hint="School" />
<AutoCompleteTextView
android:id="#+id/educ"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:completionThreshold="1"
android:drawableLeft="#drawable/ic_baseline_article_24"
android:drawablePadding="5dp"
android:hint="Educational Attainment" />
<AutoCompleteTextView
android:id="#+id/etcourse"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:completionThreshold="1"
android:drawableLeft="#drawable/ic_baseline_article_24"
android:drawablePadding="5dp"
android:hint="Course" />
</LinearLayout>
<LinearLayout
android:id="#+id/linear3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintTop_toBottomOf="#+id/linear2">
<EditText
android:id="#+id/etPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:drawableLeft="#drawable/ic_baseline_lock_24"
android:drawablePadding="5dp"
android:hint="Password"
android:inputType="textPassword" />
<EditText
android:id="#+id/etPasswordconfirm"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:drawableLeft="#drawable/ic_baseline_lock_open_24"
android:drawablePadding="5dp"
android:hint="Confirm Password"
android:inputType="textPassword" />
<Button
android:id="#+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="24dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginBottom="10dp"
android:background="#drawable/button"
android:gravity="center"
android:hint="SIGN UP"
android:textColorHint="#FDFCFC"
app:backgroundTint="#315E8C" />
<ProgressBar
android:id="#+id/progressBar2"
style="?android:attr/progressBarStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:visibility="invisible" />
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
ANDROID MANIFEST
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.trtalpha17">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.TRTAlpha17"
>
<activity android:name=".Register_Tutor">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".Login" />
<activity android:name=".RegisterStudent" />
<activity android:name=".RegistrationHome" />
<activity android:name=".MainActivity" />
</application>
</manifest>

Did you clean and rebuild your project or Invalid caches/restart from IDE?You will find it in under File menu.
It seems like your code is fine , so I decided to run in IDE its compiling and running perfectly .
Firebase console-
So you can do some checks in your side -
1.
setContentView(R.layout.activity_register_tutor2);
is layout.activity_register_tutor2 your main/default layout? Or any other layout`?
2.
if(fAuth.getCurrentUser() != null){
startActivity(new Intent(getApplicationContext(),MainActivity.class));
finish();
}
If you already sign in at least one time , this code will take you in MainActivity . Is that blank activity MainActivity? Make sure . You did not share your layout file of MainActivity , so I'm not sure .
You can Implement logout to test/debug your app easier by -
private Button mLogOutBtn;
mLogOutBtn = findViewById(R.id.log_out_btn);
mAuth = FirebaseAuth.getInstance();
mLogOutBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mAuth.signOut();
startActivity(new Intent(MainActivity.this, Register_Tutor.class));
finish();
}
});

Crashes probably due to bad activity layout

I've been developing an application and it has been working good until I added a LinearLayout (id = 'toolbar') and some functions in that activity's corresponding Java file. Here are my codes:
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.com.myapplication">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".EditPhotoActivity"
android:parentActivityName=".MainActivity">
<meta-data android:name="android.support.PARENT_ACTIVITY"
android:value=".MainActivity" />
</activity>
</application>
</manifest>
MainActivty is working good and I don't think the problem is in it. Please let me know if you want me add its code.
EditPhotoActivity.java
package com.example.com.myapplication;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.Toast;
import java.io.IOException;
public class EditPhotoActivity extends AppCompatActivity {
public ImageView image_view = findViewById(R.id.image_display) ;
public boolean toolbar_is_open = false ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_photo);
ImageView imageView = findViewById(R.id.image_display);
Intent intent = getIntent();
Uri content;
if(intent.getStringExtra(MainActivity.DATA_TYPE).equals("Uri")) {
Bundle bundle = intent.getExtras();
if(bundle != null) {
content = (Uri) bundle.get(MainActivity.IMAGE_KEY);
try {
Bitmap bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), content);
imageView.setImageBitmap(bitmap);
} catch(IOException e) {
e.printStackTrace();
Toast.makeText(this, "Failed to fetch image data!", Toast.LENGTH_LONG).show() ;
}
}
} else if(intent.getStringExtra(MainActivity.DATA_TYPE).equals("Bundle")) {
Bundle bundle = intent.getBundleExtra(MainActivity.IMAGE_KEY);
Bitmap bitmap = (Bitmap)bundle.get("data");
imageView.setImageBitmap(bitmap);
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.publish_menu, menu);
return true ;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.share_button:
// Save the photo
break;
case R.id.save_button:
// Open Share Photo Activity
break;
}
return super.onOptionsItemSelected(item);
}
private void setToolbarState(boolean open) {
LinearLayout toolbar = findViewById(R.id.toolbar);
LinearLayout.LayoutParams params = (LinearLayout.LayoutParams)toolbar.getLayoutParams();
params.height = open? 50 : 0;
toolbar.setLayoutParams(params);
toolbar_is_open = open ;
}
public void openRotateToolbar(View view) {
Button right = new Button(this), left = new Button(this);
right.setText(R.string.right); left.setText(R.string.left);
right.setBackgroundResource(R.drawable.custom_button);
left.setBackgroundResource(R.drawable.custom_button);
right.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View view) {
image_view.setRotation(90f);
}
});
left.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View view) {
image_view.setRotation(-90f);
}
});
if(!toolbar_is_open)
setToolbarState(true);
}
public void closeToolbar(View view) {
if(toolbar_is_open)
setToolbarState(false);
}
}
activity_edit_photo.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.com.myapplication.EditPhotoActivity"
tools:layout_editor_absoluteY="81dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="fill_parent"
android:layout_alignParentBottom="true"
android:weightSum="2"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="#+id/image_display"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:adjustViewBounds="true"
android:background="#color/black"
android:padding="0dp"
android:scaleType="fitCenter"
app:layout_constraintBottom_toTopOf="#+id/toolbar"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/ic_launcher_background"
tools:ignore="contentDescription" />
<LinearLayout
android:id="#+id/toolbar"
android:layout_width="0dp"
android:layout_height="0dp"
android:background="#111"
android:orientation="horizontal"
app:layout_constraintBottom_toTopOf="#+id/scrollView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintStart_toStartOf="parent">
<Button
android:id="#+id/button4"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="#string/close"
android:background="#drawable/custom_button"
android:textColor="#fff"
android:onClick="closeToolbar" />
</LinearLayout>
<HorizontalScrollView
android:id="#+id/scrollView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:background="#color/darkGrey"
android:minHeight="?attr/actionBarSize"
android:theme="?attr/actionBarTheme"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:orientation="horizontal">
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/custom_button"
android:text="#string/add_sticker"
android:textColor="#fff"
android:textSize="12sp"
tools:ignore="ButtonStyle" />
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:layout_marginTop="-15dp"
android:background="#drawable/custom_button"
android:gravity="center"
android:text="#string/create_sticker"
android:textSize="12sp"
tools:ignore="ButtonStyle" />
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/custom_button"
android:gravity="center"
android:text="#string/cut_sticker"
android:textSize="12sp"
tools:ignore="ButtonStyle" />
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/custom_button"
android:gravity="center"
android:text="#string/apply_filter"
android:textSize="12sp"
tools:ignore="ButtonStyle" />
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/custom_button"
android:gravity="center"
android:text="#string/rotate"
android:textSize="12sp"
tools:ignore="ButtonStyle"
android:onClick="openRotateToolbar" />
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/custom_button"
android:gravity="center"
android:text="#string/flip"
android:textSize="12sp"
tools:ignore="ButtonStyle" />
<Button
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/custom_button"
android:gravity="center"
android:text="#string/crop"
android:textSize="12sp"
tools:ignore="ButtonStyle" />
</LinearLayout>
</HorizontalScrollView>
</android.support.constraint.ConstraintLayout>
</RelativeLayout>
</android.support.constraint.ConstraintLayout>
I am not getting any errors but when the app is transitioning to EditPhoto Activity it crashes. Please let me know if you need me to provide you with any other information.
Note: I can not post the logcat because I am not using ADB and I am not using a computer that is all mine (it's my family's) so I don't want to enable x-vt in BIOS and so I am not able to use an Emulator also. To test my app I build the apk then I install it on my phone.

I have found my mistake. I will let this answer here for anyone that comes into the same problem.
The line:
public ImageView image_view = findViewById(R.id.image_display) ;
causes NullPointerException because at the time the app is opening the activity it does not yet have all the view and id's. It gets them only when it calls onCreate so I replaced the line to
public ImageView image_view ;
and inside onCreate after the super.onCreate(savedInstanceState) and the setContentView(R.layout.activity_edit_photo) calls I added
image_view = findViewById(R.id.image_display) ;

Cant see all of my buttons on a phone

**I am making some app and cant see a button that I have created (this is when running the app on my phone) ,but if I run it on the emulator I can see everything - the button that I can't see on my phone is the clicked button (its id is "startBtn").
**
Here is my layout :
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:background="#798"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="unleashed.myprefs.MainActivity">
<TextView
android:id="#+id/textView"
android:layout_width="match_parent"
android:layout_height="90dp"
android:text="hello"
android:background="#ff14"
/>
<Button
android:id="#+id/startBtn"
android:text="start"
android:layout_below="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="addOne"
/>
<Button
android:id="#+id/resetBtn"
android:text="restart"
android:layout_below="#+id/textView"
android:layout_alignParentRight="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="restart"
/>
</RelativeLayout>
And this is my main activity
package unleashed.myprefs;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
Button restartNums;
SharedPreferences prefs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
prefs = getSharedPreferences("main", MODE_PRIVATE);
}
private int getNum(){
return prefs.getInt("num",1);
}
private void setNum(int num){ // put the number into my shared preference
prefs.edit().putInt("num", num).apply();
}
public void addOne(View v) { //adding number to the starting button
int num = getNum();
((Button)v).setText("Clicked " + num);
setNum(num + 1);
}
public void restart(View v){
restartNums = (Button) findViewById(R.id.startBtn);
prefs.edit().remove("num").apply();
restartNums.callOnClick();
}
}
I will appreciate any help.

AlignParentEnd should be used in ResetButton.( Not sure )
(Alternative) If you trying to have two buttons in the same row, you can try this layout..
`
<TextView
android:id="#+id/textView"
android:layout_width="match_parent"
android:layout_height="90dp"
android:text="hello"
android:background="#ff14"
/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation = "horizontal"
android:weightsum="2"
android:layout_below="#+id/textView">
<Button
android:id="#+id/startBtn"
android:text="start"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:onClick="addOne"
/>
<Button
android:id="#+id/resetBtn"
android:text="restart"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:onClick="restart"/>
`

why my app button isn't navigating to next page in android studio using java

I am new to app development, I am stuck on this following example in my book.
Can some one please help me that why my play button is not working? After clicking on the play button the game should start and it should navigate to next activity.
Main page code
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.packtpub.mathgamechapter3a.MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="My Math Game"
android:id="#+id/textView"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="25dp"
android:textSize="30sp" />
<ImageView
android:layout_width="150dp"
android:layout_height="150dp"
android:id="#+id/imageView"
android:src="#mipmap/ic_launcher"
android:layout_below="#+id/textView"
android:layout_centerHorizontal="true"
android:layout_marginTop="38dp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Play"
android:id="#+id/buttonPlay"
android:layout_marginTop="28dp"
android:layout_below="#+id/imageView"
android:layout_alignRight="#+id/button2"
android:layout_alignEnd="#+id/button2"
android:layout_alignLeft="#+id/button2"
android:layout_alignStart="#+id/button2" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="High Scores"
android:id="#+id/button2"
android:layout_below="#+id/buttonPlay"
android:layout_centerHorizontal="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Quit"
android:id="#+id/button3"
android:layout_below="#+id/button2"
android:layout_alignRight="#+id/buttonPlay"
android:layout_alignEnd="#+id/buttonPlay"
android:layout_alignLeft="#+id/button2"
android:layout_alignStart="#+id/button2" />
</RelativeLayout>
Java code
package com.packtpub.mathgamechapter3a;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends Activity implements View.OnClickListener{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button buttonPlay = (Button)findViewById(R.id.buttonPlay);
buttonPlay.setOnClickListener(this);
}
#Override
public void onClick(View view) {
Intent i;
i = new Intent(this, GameActivity.class);
startActivity(i);
}
}
Game page where it should navigate
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.packtpub.mathgamechapter3a.GameActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="2"
android:id="#+id/textPartA"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="24dp"
android:textSize="70sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="x"
android:id="#+id/textOperator"
android:layout_alignTop="#+id/textPartA"
android:layout_centerHorizontal="true"
android:textSize="70sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="2"
android:id="#+id/textPartB"
android:layout_alignTop="#+id/textOperator"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:textSize="70sp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="="
android:id="#+id/textView4"
android:layout_below="#+id/textOperator"
android:layout_centerHorizontal="true"
android:layout_marginTop="92dp"
android:textSize="70sp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="2"
android:id="#+id/buttonChoice1"
android:layout_below="#+id/textView4"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="99dp"
android:textSize="40sp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="4"
android:id="#+id/buttonChoice2"
android:layout_alignTop="#+id/buttonChoice1"
android:layout_centerHorizontal="true"
android:textSize="40sp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="6"
android:id="#+id/buttonChoice3"
android:layout_alignTop="#+id/buttonChoice2"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:textSize="40sp" />
</RelativeLayout>
Java code
package com.packtpub.mathgamechapter3a;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class GameActivity extends Activity implements View.OnClickListener{
int correctAnswer;
Button buttonObjectChoice1;
Button buttonObjectChoice2;
Button buttonObjectChoice3;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//The next line loads our UI design to the screen
setContentView(R.layout.activity_game);
//Here we initialize all our variables
int partA = 9;
int partB = 9;
correctAnswer = partA * partB;
int wrongAnswer1 = correctAnswer - 1;
int wrongAnswer2 = correctAnswer + 1;
/*Here we get a working object based on either the button
or TextView class and base as well as link our new objects
directly to the appropriate UI elements that we created previously*/
TextView textObjectPartA = (TextView)findViewById(R.id.textPartA);
TextView textObjectPartB = (TextView)findViewById(R.id.textPartB);
buttonObjectChoice1 = (Button)findViewById(R.id.buttonChoice1);
buttonObjectChoice2 = (Button)findViewById(R.id.buttonChoice2);
buttonObjectChoice3 = (Button)findViewById(R.id.buttonChoice3);
//Now we use the setText method of the class on our objects
//to show our variable values on the UI elements.
textObjectPartA.setText("" + partA);
textObjectPartB.setText("" + partA);
//which button receives which answer, at this stage is arbitrary.
buttonObjectChoice1.setText("" + correctAnswer);
buttonObjectChoice2.setText("" + wrongAnswer1);
buttonObjectChoice3.setText("" + wrongAnswer2);
buttonObjectChoice1.setOnClickListener(this);
buttonObjectChoice2.setOnClickListener(this);
buttonObjectChoice3.setOnClickListener(this);
}//onCreate ends here
#Override
public void onClick(View view) {
//declare a new int to be used in all the cases
int answerGiven=0;
switch (view.getId()) {
case R.id.buttonChoice1:
//initialize a new int with the value contained in buttonObjectChoice1
//Remember we put it there ourselves previously
answerGiven = Integer.parseInt("" + buttonObjectChoice1.getText());
//is it the right answer?
if(answerGiven==correctAnswer) {//yay it's the right answer
Toast.makeText(getApplicationContext(),
"Well done!", Toast.LENGTH_LONG).show();
}else{//uh oh!
Toast.makeText(getApplicationContext(),
"Sorry that's wrong", Toast.LENGTH_LONG).show();
}
break;
case R.id.buttonChoice2:
//same as previous case but using the next button
answerGiven = Integer.parseInt("" + buttonObjectChoice2.getText());
if(answerGiven==correctAnswer) {
Toast.makeText(getApplicationContext(), "Well done!",
Toast.LENGTH_LONG).show();
}else{
Toast.makeText(getApplicationContext(),
"Sorry that's wrong", Toast.LENGTH_LONG).show();
}
break;
case R.id.buttonChoice3:
//same as previous case but using the next button
answerGiven = Integer.parseInt("" + buttonObjectChoice3.getText());
if(answerGiven==correctAnswer) {
Toast.makeText(getApplicationContext(), "Well done!",
Toast.LENGTH_LONG).show();
}else{
Toast.makeText(getApplicationContext(),"Sorry that's wrong",
Toast.LENGTH_LONG).show();
}
break;
}
}
}

i checked your code it is correct .
I think you forget to register your activity in manifests
please check that

well you need to do a if statement on the being clicked on.
if(view.getId() == R.id.buttonPlay)
{
Intent intent = new Intent(getBaseContext(), GameActivity.class);
startActivity(intent);
}
also make sure game activity is registered in the manifest file.

Intent in = getIntent();
is missing..
the 2nd activity should contain this line
also add this
if(view.getId() == R.id.buttonPlay)
{
Intent inte = new Intent(MainActivity.this, GameActivity.class);
startActivity(intent);
}
and do register in the manifest file

The app I am working on crashes when i try to go from one intent to the other, I've tried everything. code:

The Start class:
It as a very simple program, i designed two screen, and by pressing a button on the main screen i wanted the app to open the second screen, but unfortunately its not happening, the app keeps crushing over and over again.
package com.example.snakesnladders;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
public class Start extends Activity implements OnClickListener {
Button start, settings;
TextView snakes, and, ladders;
ImageView snakePic;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainscreen);
init();
}
#Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
}
private void init() {
start = (Button) findViewById(R.id.btStart);
settings = (Button) findViewById(R.id.btSettings);
snakes = (TextView) findViewById(R.id.tvSnakes);
and = (TextView) findViewById(R.id.tvAnd);
ladders = (TextView) findViewById(R.id.tvLadders);
snakePic = (ImageView) findViewById(R.id.snakePic);
start.setOnClickListener(this);
settings.setOnClickListener(this);
}
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.btStart:
break;
case R.id.btSettings:
Intent i = new Intent("com.example.snakesnladders.SET");
startActivity(i);
break;
default: break;
}
}
}
The Set class:
package com.example.snakesnladders;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
public class Set extends Activity implements OnClickListener {
Button sound, difficulty, back;
TextView settings;
ImageView snakePic;
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.setscreen);
init();
}
private void init() {
sound = (Button) findViewById(R.id.btSound);
difficulty = (Button) findViewById(R.id.btDifficulty);
back = (Button) findViewById(R.id.btBack);
settings = (TextView) findViewById(R.id.tvSetPage);
snakePic = (ImageView) findViewById(R.id.setSnakePic);
sound.setOnClickListener(this);
difficulty.setOnClickListener(this);
back.setOnClickListener(this);
}
#Override
public void onClick(View view) {
// TODO Auto-generated method stub
switch (view.getId()) {
case R.id.btSound:
String s = sound.getText().toString();
if (s.equals("Sound:on")) {
sound.setText("Sound:off");
ControlSounds.player.stop();
} else {
sound.setText("Sound:on");
ControlSounds.player.start();
}
break;
case R.id.btDifficulty:
break;
case R.id.btBack:
Intent i = new Intent(Set.this, Start.class);
startActivity(i);
finish();
break;
}
}
#Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
}
}
The manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.snakesnladders"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".Start"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".Set"
android:label="#string/app_name" >
<intent-filter>
<action android:name="com.example.snakesnladders.SET" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
mainscreen.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/black"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="175dp"
android:orientation="vertical" >
<TextView
android:id="#+id/tvSnakes"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_gravity="center"
android:text="Snakes"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#color/green"
android:textSize="30sp" />
<TextView
android:id="#+id/tvAnd"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_gravity="center"
android:text="#string/and"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#color/green"
android:textSize="30sp" />
<TextView
android:id="#+id/tvLadders"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_gravity="center"
android:text="Ladders"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#color/green"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="125dp"
android:orientation="vertical" >
<Button
android:id="#+id/btStart"
android:layout_width="250dp"
android:layout_height="60dp"
android:layout_gravity="center"
android:background="#drawable/buttonshape"
android:shadowColor="#A8A8A8"
android:shadowDx="0"
android:shadowDy="0"
android:shadowRadius="10"
android:text="Start New Game"
android:textColor="#FFFFFF"
android:textSize="30sp" />
<Button
android:id="#+id/btSettings"
android:layout_width="250dp"
android:layout_height="60dp"
android:layout_gravity="center"
android:background="#drawable/buttonshape"
android:shadowColor="#A8A8A8"
android:shadowDx="0"
android:shadowDy="0"
android:shadowRadius="10"
android:text="Settings"
android:textColor="#FFFFFF"
android:textSize="30sp" />
</LinearLayout>
<ImageView
android:id="#+id/snakePic"
android:layout_width="wrap_content"
android:layout_height="125dp"
android:layout_gravity="center"
android:layout_weight="0.47"
android:background="#color/black"
android:src="#drawable/snake" />
</LinearLayout>
setscreen.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/black"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/black"
android:orientation="vertical" >
<TextView
android:id="#+id/tvSetPage"
android:layout_width="wrap_content"
android:layout_height="60dp"
android:layout_gravity="center"
android:text="Settings"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#color/green"
android:textSize="40sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/black"
android:orientation="vertical" >
<Button
android:id="#+id/btSound"
android:layout_width="250dp"
android:layout_height="60dp"
android:layout_gravity="center"
android:background="#drawable/buttonshape"
android:shadowColor="#A8A8A8"
android:shadowDx="0"
android:shadowDy="0"
android:shadowRadius="10"
android:text="Sound:on"
android:textColor="#FFFFFF"
android:textSize="30sp" />
<Button
android:id="#+id/btDifficulty"
android:layout_width="250dp"
android:layout_height="60dp"
android:layout_gravity="center"
android:background="#drawable/buttonshape"
android:shadowColor="#A8A8A8"
android:shadowDx="0"
android:shadowDy="0"
android:shadowRadius="10"
android:text="Difficulty:easy"
android:textColor="#FFFFFF"
android:textSize="30sp" />
<Button
android:id="#+id/btBack"
android:layout_width="250dp"
android:layout_height="60dp"
android:layout_gravity="center"
android:background="#drawable/buttonshape"
android:shadowColor="#A8A8A8"
android:shadowDx="0"
android:shadowDy="0"
android:shadowRadius="10"
android:text="Back To Menu"
android:textColor="#FFFFFF"
android:textSize="30sp" />
</LinearLayout>
<ImageView
android:id="#+id/setSnakePic"
android:layout_width="wrap_content"
android:layout_gravity="center"
android:layout_weight="0.25"
android:background="#color/black"
android:src="#drawable/snake1" />
</LinearLayout>

Change this
Intent i = new Intent("com.example.snakesnladders.SET");
startActivity(i);
To
Intent i = new Intent(Start.this,Set.class);
startActivity(i);
And Change this
<activity
android:name=".Set"
android:label="#string/app_name" >
<intent-filter>
<action android:name="com.example.snakesnladders.SET" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
To
<activity
android:name=".Set"
android:label="#string/app_name" >
</activity>
Use Explicit Intent's
To know why read
http://developer.android.com/guide/components/intents-filters.html
Explicit intents specify the component to start by name (the
fully-qualified class name). You'll typically use an explicit intent
to start a component in your own app, because you know the class name
of the activity or service you want to start. For example, start a new
activity in response to a user action or start a service to download a
file in the background.