Develop Reference

Getting error in changing co-ordinates of imageview in android studio

I am a beginner to android. I want to slide a slidebar in a horizontal linear layout but when I run the code, the application ends giving error FallingBall keeps stopping
My xml:
<?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=".MainActivity">
<LinearLayout
android:id="#+id/linearLayout2"
android:layout_width="0dp"
android:layout_height="0dp"
android:orientation="vertical"
android:weightSum="100"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:id="#+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="72"
android:orientation="horizontal" >
<TextView
android:id="#+id/textView2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Hello" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="8"
android:orientation="horizontal">
<ImageView
android:id="#+id/slideBar"
android:layout_width="100dp"
android:layout_height="match_parent"
app:srcCompat="#android:drawable/bottom_bar" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="20"
android:orientation="horizontal">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageButton
android:id="#+id/leftBut"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:background="#android:color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/left_but"
android:onClick="hitLeft"/>
<ImageButton
android:id="#+id/rightBut"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:background="#android:color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/right_but"
android:onClick="hitRight"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</LinearLayout>
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
My java file is like this:
package com.example.fallingball;
import androidx.appcompat.app.AppCompatActivity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
public class MainActivity extends AppCompatActivity {
ImageView s = findViewById(R.id.slideBar);
float x = s.getX();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}
void hitLeft(View view){
x--;
s.setX(30);
}
void hitRight(View view){
x++;
s.setX(40);
}
}
Note: leftBut and rightBut are two Image button and I have copied the images to the drawable folder so if you are trying this code on your system, make sure you adjust this else it will show you Image not found or so...

In MainActivity.java you should initialize your value into onCreate() method
ImageView s;
float x;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
s = findViewById(R.id.slideBar);
x = s.getX();
}

Well, I found my own mistake. The thing what hossein answered earlier was right but the application was still crashing. Actually the problem was coming that I was triggering the methods hitLeft and hitRight which were not initialized as public. That was the mistake and now it is working alright...

Image Button resizing

I'm setting up an image button in Android Studio. All looks fine in design view, but when the application is loaded, the image button is moved to the top left corner and reduced in size?
Shown below:
Design View
XML Code - current
<?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=".ui.PhysicalActivity">
<ImageButton
android:id="#+id/btnImageGallery"
android:layout_width="200dp"
android:layout_height="300dp"
android:layout_marginStart="8dp"
android:onClick="onImageGalleryClicked"
android:src="#drawable/placeholder"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.921"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.74" />
</android.support.constraint.ConstraintLayout>
PhysicalActivity Code
package com.example.futura.ui;
import android.content.Intent;
import android.net.Uri;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import com.example.futura.R;
import java.io.File;
public class PhysicalActivity extends AppCompatActivity {
public static final int IMAGE_GALLERY_REQUEST = 20;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_physical1);
}
public void onImageGalleryClicked(View v){
// invoke the image gallery using an implict intent.
Intent photoPickerIntent = new Intent(Intent.ACTION_PICK);
File pictureDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
String pictureDirectoryPath = pictureDirectory.getPath();
// finally, get ui represenation
Uri data = Uri.parse(pictureDirectoryPath);
// set the data and type, get all image types
photoPickerIntent.setDataAndType(data, "image/*" );
startActivityForResult(photoPickerIntent, IMAGE_GALLERY_REQUEST);
}
}
Preview
Does any one have any advice on correcting this?

Try add layout_constraintHorizontal_bias and layout_constraintStart_toStartOf
<?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">
<ImageButton
android:id="#+id/btnImageGallery"
android:layout_width="200dp"
android:layout_height="300dp"
android:layout_marginStart="8dp"
android:onClick="onImageGalleryClicked"
android:src="#drawable/placeholder"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.921"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.74" />
</android.support.constraint.ConstraintLayout>

Remove margins (start, top, bottom, end) and adjust layout_constraintHorizontal_bias, layout_constraintVertical_bias to achieve desired result.
<android.support.v7.widget.AppCompatImageButton
android:id="#+id/startSyncButton"
android:layout_width="200dp"
android:layout_height="300dp"
app:layout_constraintHorizontal_bias="0.9"
app:layout_constraintVertical_bias="0.7"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />

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"/>
`

Method is missing or has incorrect signature

I am making a simple app in which context view changes and then a toast message is displayed as input given by user. I don't understand why the app keeps on crashing when changing the context view.
Also Android studio gives this warning:
Method "Toaster" is missing in "FirstActivity" or has incorrect signature.
Here is my code:
activity_me_clicked.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="#string/welcome"
android:textSize="36sp" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:paddingLeft="7dp"
android:paddingRight="7dp"
android:text="#string/intro"
android:textSize="24sp" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:baselineAligned="false">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:orientation="vertical">
<EditText
android:id="#+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="7dp"
android:layout_marginEnd="7dp"
android:layout_marginTop="10dp"
android:ems="10"
android:hint="Name"
android:inputType="textPersonName"
tools:ignore="HardcodedText" />
<Button
android:id="#+id/named"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:paddingBottom="10dp"
android:paddingTop="10dp"
android:onClick="MainProcess"
android:text="#string/done" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:orientation="horizontal"
tools:ignore="UselessLeaf"></LinearLayout>
</LinearLayout>
</LinearLayout>
FirstActivity.Java:
package com.example.nautatvanavlakha.abcd;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
public class FirstActivity extends AppCompatActivity {
public static String owner_string;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_me_clicked);
}
public void MainProcess(View view) {
final String TAG="DEBUG";
Log.d(TAG,"At least process started");
EditText owner = (EditText) findViewById(R.id.name);
owner_string = owner.getText().toString();
Log.d(TAG,"owner name stored");
TextView textView = (TextView) findViewById(R.id.welcome);
textView.setText("Hi " + owner_string + ".");
Log.d(TAG,"owner name is set");
setContentView(R.layout.activity_main_screen);
Log.d(TAG,"content shown");
}
}
activity_main_screen.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:orientation="vertical">
<TextView
android:id="#+id/welcome"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<TextView
android:id="#+id/textView4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/what_would_you_like_me_to_do_today"
android:textSize="18sp" />
<Button
android:id="#+id/Cam"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:padding="0dp"
android:paddingTop="15dp"
android:text="#string/camera" />
<Button
android:id="#+id/Mus"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:padding="0dp"
android:paddingTop="15dp"
android:text="#string/music" />
<Button
android:id="#+id/QR"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:padding="0dp"
android:paddingTop="15dp"
android:text="#string/scanQR" />
<EditText
android:id="#+id/toastText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="#string/order"
android:inputType="textPersonName" />
<Button
android:id="#+id/toaster"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:onClick="toaster"
android:padding="0dp"
android:paddingTop="15dp"
android:text="#string/toast"
android:layout_marginEnd="100dp"
android:layout_gravity="center"/>
</LinearLayout>
MainScreen.java:
package com.example.nautatvanavlakha.abcd;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class MainScreen extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_screen);
}
public void toaster(View view){
EditText toast = (EditText)findViewById(R.id.toastText);
String final_toast = toast.getText().toString();
Toast.makeText(getApplicationContext(), final_toast, Toast.LENGTH_SHORT).show();
}
}
EDIT: As suggested, I moved the toaser function to FirstActivity.Java and deleted the MainScreen.java file as it becomes pointless to keep it. But the major problem is when I press the button (id named) the app keeps stopping.
EDIT2: I found that setContentView(R.layout.activity_main_screen) in FirstActivity.Java needs to be above this code
TextView textView = (TextView) findViewById(R.id.welcome);
textView.setText("Hi " + owner_string + ".");
Log.d(TAG,"owner name is set");
so that Activity has access to all the layout components. Thanks solved :)

You replaced the content view in the first activity with a layout that include the onClick attribute, but you have no public void toaster(View view) method there.
So, either don't use setContentView a second time, or implement that method on both Activities.
The recommended way to replace the view is Fragments, by the way

This is a wrong way to change the contents of your Activity, The main problem here is that you have onClick attribute set to "toaster", And you don't have a function called "toaster" in your FirstActivity.
Beside that, The MainScreen Activity in your code will never be used.
So, Your problem is that you set the FirstActivity contents to "activity_main_screen.xml", And FirstActivity doesn't have "toaster" method in it, When you change the context, the Activity will try to find toaster method and the app will crash because the method doesn't exist in FirstActivity.
You can solve this problem by making a method called "toaster" inside FirstActivity, But
This is a very bad practice, You can use Fragments instead, Or you can use Intent to move to another activity.
Some useful links about Fragments:
https://developer.android.com/guide/components/fragments.html
https://www.tutorialspoint.com/android/android_fragments.htm
https://examples.javacodegeeks.com/android/core/app/fragment/android-fragments-example/
Why should I use fragment in Android?

Android Java programming error while switching screens

As mentioned in title, I face an error when I compile and try to run the following program in my phone.
Code:
(File mainActivity.java)
package com.game.myapp;
import android.app.*;
import android.os.*;
import android.content.Intent;
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void VillageOnClick() {
Intent intent = new Intent(MainActivity.this, VillageView.class);
startActivity(intent);
}
}
(File VillageView.java)
package com.game.myapp;
import android.app.*;
import android.os.*;
public class VillageView extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.village_view);
}
}
(File main.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:gravity="center">
<LinearLayout
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:orientation="horizontal"
android:layout_margin="10dp"
android:layout_gravity="bottom">
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="village"
android:onClick="VillageOnClick"/>
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="research"/>
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="battle"/>
</LinearLayout>
</LinearLayout>
(File village_view.xml)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal"
android:gravity="center">
<LinearLayout
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:orientation="horizontal"
android:layout_gravity="bottom"
android:layout_margin="10dp">
<Button
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="Button"/>
</LinearLayout>
</LinearLayout>
Note:I write, compile, install and run the app on my android phone only using an app.
Note2: both the xml files are located in res/layout and most probable are not the cause of the error.
Note3: I do not understand Intent. Knowledge about the same is always appreciated.
Thanks in advance.
PS. Suggestions and change in format of code is always accepted happily.
Madworks.

you need to add the View in the VillageOnClick
public void VillageOnClick(View v) {
Intent intent = new Intent(MainActivity.this, VillageView.class);
startActivity(intent);
}