Develop Reference

Android Studio: FATAL EXCEPTION: main while getting user inputs

I was trying to use user input name for later use but Once i run the app this is closed by saying unfortunately your app has stopped. I have provided Main activity,Layout xml and android manifest codes. Please anyone answer this . I am newbie in android and cant figure out the error.
Main_activity
package rupakthapa.droiddynasty.com.interactivestory2;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import static android.R.attr.duration;
import static android.R.attr.name;
public class MainActivity extends AppCompatActivity {
private EditText mNameField;
private Button mButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mNameField = (EditText) findViewById(R.id.nameField);
mButton = (Button) findViewById(R.id.startButton);
mButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String a= mNameField.getText().toString();
Context context = getApplicationContext();
int length = Toast.LENGTH_LONG;
Toast toast = Toast.makeText(context, a, length);
toast.show();
}
});
}
}
XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/activity_main"
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="rupakthapa.droiddynasty.com.interactivestory2.MainActivity">
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:srcCompat="#mipmap/ic_launcher"
android:id="#+id/imageView"
android:adjustViewBounds="true"
android:scaleType="fitXY"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="149dp"
android:contentDescription="startImage"/>
<TextView
android:layout_width="match_parent"
android:id="#+id/nameField"
android:hint="Enter YOur Name"
android:layout_above="#+id/startButton"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="11dp"
android:maxLength="30"
android:layout_marginLeft="10dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_height="wrap_content"
android:textSize="16sp"/>
<Button
android:text="Start your adventure"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/startButton"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"/>
</RelativeLayout>
Android Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest package="rupakthapa.droiddynasty.com.interactivestory2"
xmlns:android="http://schemas.android.com/apk/res/android">
<application
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:supportsRtl="true"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>

There is a problem here. You dont have EditText in your layout.
mNameField = (EditText) findViewById(R.id.nameField);
In your layout you should change TextView to EditText
<EditText
android:layout_width="match_parent"
android:id="#+id/nameField"
android:hint="Enter YOur Name"
android:layout_above="#+id/startButton"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="11dp"
android:maxLength="30"
android:layout_marginLeft="10dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_height="wrap_content"
android:textSize="16sp"/>

How do i change activity on a button click android

I have an ImageButton that when I want it to be pressed to launch a second Activity. The second activity is called "Dust 2" as seen in my android manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="pete.smokesapp" >
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".homepage"
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=".Dust2"
android:label="#string/title_activity_dust2" >
</activity>
</application>
</manifest>
I tried following a guide online but got me as far as this stage now my app crashed on launch.
package pete.smokesapp;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Toast;
public class homepage extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_homepage);
findViewById(R.id.imgDust2).setOnClickListener((View.OnClickListener) this);
}
public void imgDust2(View view) {
switch (view.getId()){
case R.id.imgDust2:
Toast.makeText(this, "Dust 2 Clicked", Toast.LENGTH_LONG ).show();
break;
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_homepage, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
Here is also my main activity, this is the activity with the ImageButton, i am also new to this so sorry if I seem clueless.
<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" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity">
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:fillViewport="true">
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:weightSum="1">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Maps"
android:id="#+id/txtMaps"
android:layout_weight="0.44" />
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgDust2"
android:clickable="false"
android:src="#drawable/dust2"
android:layout_above="#+id/imgOverpass"
android:layout_alignLeft="#+id/imgOverpass"
android:layout_alignStart="#+id/imgOverpass"
android:layout_marginBottom="10dp" />
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgInferno"
android:layout_below="#+id/txtOverpass"
android:layout_alignLeft="#+id/imgOverpass"
android:layout_alignStart="#+id/imgOverpass"
android:layout_marginBottom="10dp"
android:src="#drawable/inferno" />
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgOverpass"
android:src="#drawable/overpass"
android:layout_marginBottom="10dp"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true" />
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgMirage"
android:clickable="false"
android:src="#drawable/mirage"
android:layout_above="#+id/imgOverpass"
android:layout_alignLeft="#+id/imgOverpass"
android:layout_alignStart="#+id/imgOverpass"
android:layout_marginBottom="10dp" />
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgCache"
android:clickable="false"
android:src="#drawable/cache"
android:layout_above="#+id/imgOverpass"
android:layout_alignLeft="#+id/imgOverpass"
android:layout_alignStart="#+id/imgOverpass"
android:layout_marginBottom="10dp" />
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgNuke"
android:clickable="false"
android:src="#drawable/nuke"
android:layout_above="#+id/imgOverpass"
android:layout_alignLeft="#+id/imgOverpass"
android:layout_alignStart="#+id/imgOverpass"
android:layout_marginBottom="10dp" />
</LinearLayout>
</ScrollView>
</RelativeLayout>

There are two methods available in android using which you can go from one Activity to another.
1. Use button.setOnClickListener()
Create a button in xml file.
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
Now set event listener for the button in your .class file
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//set the event you want to perform when button is clicked
//you can go to another activity in your app by creating Intent
Intent intent = new Intent(getApplicationContext, Activity2.class);
startActivity(intent);
}
});
2. Use <android:onClick="goNext">
Put the onClick as the attribute of the button you have created in xml file.
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
android:onClick="goNext" />
Now in your .class file define an event for that button as,
goNext() {
Intent intent = new Intent(getApplicationContext, Activity2.class);
startActivity(intent);
}

In your first activity do this:
Button button = (Button) findViewById(R.id.imgDust2);
button.setOnClickListener(new View.OnClickListener () {
#Override
public void onClick(View v){
Intent intent = new Intent(v.getContext(), dust2.class);
startActivity(intent);
}
});

Try the following:
Add implements OnClickListener to your class definition: public class homepage extends ActionBarActivity implements OnClickListener
An error will appear and ask you to add unimplemented methods. Do so.
Change findViewById(R.id.imgDust2).setOnClickListener((View.OnClickListener) this); to findViewById(R.id.imgDust2).setOnClickListener(this);
Place the stuff you want to do when the button is clicked into the new method that was added in step 2.

Set onClick to the xml imageView and put the name of the method:
<ImageButton
android:layout_width="350dp"
android:layout_height="150dp"
android:id="#+id/imgDust2"
android:clickable="false"
android:src="#drawable/dust2"
android:layout_above="#+id/imgOverpass"
android:layout_alignLeft="#+id/imgOverpass"
android:layout_alignStart="#+id/imgOverpass"
android:layout_marginBottom="10dp"
android:onClick="imgDust2"/>

When I click the Button it doesn't work (Android)

I am working in Eclipse, My app edit two integers and click the button so the app will show the average, but when i operate the app in my device, when i click the button it stop working and show message "application has been stopped"
XML File :
<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"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<EditText
android:id="#+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="20dp"
android:ems="10" />
<EditText
android:id="#+id/editText2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/editText1"
android:layout_centerHorizontal="true"
android:layout_marginTop="22dp"
android:ems="10" >
<requestFocus />
</EditText>
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/editText2"
android:layout_centerHorizontal="true"
android:layout_marginTop="28dp"
android:text="Button" />
<TextView
android:id="#+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#+id/button1"
android:layout_below="#+id/button1"
android:layout_marginTop="72dp"
/>
</RelativeLayout>
JAVA File :
package com.example.mine;
//import com.example.mine.R;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends Activity {
EditText num1, num2;
Button count;
TextView text;
String e1, e2;
int q, i, r;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
count = (Button) findViewById(R.id.button1);
num1 = (EditText) findViewById(R.id.editText1);
num1 = (EditText) findViewById(R.id.editText2);
text = (TextView) findViewById(R.id.text);
count.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
// TODO Auto-generated method stub
e1 = num1.getText().toString();
e2 = num2.getText().toString();
q = Integer.parseInt(e1);
i = Integer.parseInt(e2);
r = (i + q) / 2;
text.setText("the average is " + r);
// text.setText(Integer.toString(r));
// text.setText(r+"");
}
});
}
}
Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.mine"
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="com.example.mine.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Logcat is empty

Look at these two lines:
q = Integer.parseInt(e1);
i = Integer.parseInt(e2);
If e1 or e2 is not a number, parseInt will throw an IllegalArgument exception. In general, you should always expect parseInt has potential to throw an exception with user input - so a try/catch block is almost always warranted.
I don't seen any default text being set for edit1 or edit2, so without a logcat dump of the exception crash, that's my best guess.

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.

RuntimeError for activity specified on Android Manifest

I have this problem that just seems strange.
I have this Android View with six buttons and when i click on one of them(the only one with the action defined apart from the exit button), it gives me a RuntimeError.
The Activity is declared on the manifest, and this is why i don't understand my error.
Can someone please help me with this.
I would really appreciate it :)
So here's my code:
package com.example.calendar;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity implements OnClickListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View createButton = findViewById(R.id.btn_create);
View deleteButton = findViewById(R.id.btn_delete);
View moveButton = findViewById(R.id.btn_move);
View searchButton = findViewById(R.id.btn_search);
View translateButton = findViewById(R.id.btn_translate);
View exitButton = findViewById(R.id.exit);
createButton.setOnClickListener(this);
deleteButton.setOnClickListener(this);
moveButton.setOnClickListener(this);
searchButton.setOnClickListener(this);
translateButton.setOnClickListener(this);
exitButton.setOnClickListener(this);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.btn_create:
Intent i = new Intent(this, CreateAppointment.class);
startActivity(i);
break;
case R.id.exit:
finish();
break;
}
}
}
My layout is like this:
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:background="#color/background"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="225dp"
android:orientation="vertical"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin" >
<CalendarView
android:id="#+id/calendar"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<TableLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:layout_marginBottom="2dip"
android:layout_marginTop="2dip"
android:stretchColumns="*" >
<TableRow>
<Button
android:id="#+id/btn_create"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/create" />
<Button
android:id="#+id/btn_viewEdit"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/viewEdit" />
</TableRow>
<TableRow>
<Button
android:id="#+id/btn_delete"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/delete" />
<Button
android:id="#+id/btn_move"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/move" />
</TableRow>
<TableRow>
<Button
android:id="#+id/btn_search"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/search" />
<Button
android:id="#+id/btn_translate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/translate" />
</TableRow>
</TableLayout>
<Button
android:id="#+id/exit"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/exit"/>
</LinearLayout>
And the manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.calendar"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.calendar.MainActivity"
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=".CreateAppointment"
android:theme="#android:style/Theme.Dialog"
android:label="#string/create" >
</activity>
</application>
</manifest>

You have to define correctly what kind of views ares using in onCreate()
View createButton = findViewById(R.id.btn_create);
for example:
since you are using a Button:
<Button
android:id="#+id/btn_create"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/create" />
Make the cast as button:
Button createButton = (Button)findViewById(R.id.btn_create);
try this:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button createButton = (Button)findViewById(R.id.btn_create);
Button deleteButton = (Button)findViewById(R.id.btn_delete);
Button moveButton = (Button)findViewById(R.id.btn_move);
Button searchButton = (Button)findViewById(R.id.btn_search);
Button translateButton = (Button)findViewById(R.id.btn_translate);
Button exitButton = (Button)findViewById(R.id.exit);
createButton.setOnClickListener(this);
deleteButton.setOnClickListener(this);
moveButton.setOnClickListener(this);
searchButton.setOnClickListener(this);
translateButton.setOnClickListener(this);
exitButton.setOnClickListener(this);
}