Develop Reference

Why my app is crashing on clicking any of the buttons?

I am trying to use intents but on clicking any of the buttons,the app stops working and terminates.I am a beginner and I couldn't find the reason.I am providing my xml file,java file and menifest file.Please someone help.
here is my xml file:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
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"
android:orientation="vertical"
tools:context="com.example.shreya.intents.MainActivity">
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Set Alarm"
android:id="#+id/alarm"
android:onClick="setAlarm"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Map"
android:id="#+id/map"
android:onClick="seeMap"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Mail"
android:id="#+id/mail"
android:onClick="email"/>
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Email ID"
android:inputType="textCapWords"
android:id="#+id/address"/>
</LinearLayout>
And here is my .java file:
package com.example.shreya.intents;
import android.content.Intent;
import android.net.Uri;
import android.provider.AlarmClock;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.util.Locale;
import static com.example.shreya.intents.R.id.alarm;
public class MainActivity extends AppCompatActivity {
private Button mail;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void setAlarm(){
String message="Wake Up";
int hour=7;
int minutes=0;
Intent intent = new Intent(AlarmClock.ACTION_SHOW_ALARMS);
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(intent);
}
}
public void seeMap(){
String uri = String.format(Locale.ENGLISH, "geo:%f,%f", 28.699884, 77.273075);
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setData(Uri.parse(uri));
if(intent.resolveActivity(getPackageManager())!=null)
startActivity(intent);
}
public void email(){
EditText mail=(EditText)findViewById(R.id.address);
String add=mail.getText().toString();
composeEmail(add,"shreya");
}
public void composeEmail(String addresses, String subject) {
Intent intent = new Intent(Intent.ACTION_SENDTO);
intent.setData(Uri.parse("mailto:")); // only email apps should handle this
intent.putExtra(Intent.EXTRA_EMAIL, addresses);
intent.putExtra(Intent.EXTRA_SUBJECT, subject);
intent.putExtra(Intent.EXTRA_TEXT,"hello");
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(intent);
}
}
}
And finally this is my menifest file:
<?xml version="1.0" encoding="utf-8"?>
<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>
</application>

You have to add parameter View view to your onClick methods.
For example:
public void setAlarm(View view){
}
Add that parameter to other onClick methods also: email and seeMap.
Under the hood, the system uses reflection to figure out the exact onClick method in the Activity and the system uses the following exact pattern to find the method: a public void method with the specified method name in the xml onClick attribute and has a single parameter View.

OnClickListener not responding

I can't get my click listeners working. The ImageButton is retrieved correctly.
Listener (Extending my custom Activity which is setting the view):
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("UserActivity", "Loading imagebutton...");
ImageButton iButton = (ImageButton) findViewById(R.id.user_button_ratings);
Log.d("UserActivity", "Button " + iButton);
iButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.e("Button", "Image was clicked");
}
});
}
BaseActivity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(getLayoutId());
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerToggle = new ActionBarDrawerToggle((Activity) this, drawerLayout,
R.drawable.ic_drawer, 0, 0) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(R.string.app_name);
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(R.string.menu);
}
};
drawerLayout.setDrawerListener(drawerToggle);
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
layers = getResources().getStringArray(R.array.layers_array);
drawerList = (ListView) findViewById(R.id.left_drawer);
drawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.adapter_navigation, R.id.navigation_text, layers));
final BaseActivity activity = this;
drawerList.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
long arg3) {
// Do something
}
});
drawerList.setBackgroundColor(Color.LTGRAY);
}
Layout:
<ImageButton
android:id="#+id/user_button_ratings"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:background="#color/transparent"
android:scaleType="fitCenter"
android:src="#drawable/mmb_rating_big" />
Manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.panic.xenira.mmb"
android:versionCode="2"
android:versionName="0.1.1" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:theme="#style/NoActionBar" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".SearchActivity"
android:label="#string/title_activity_search" >
</activity>
<activity
android:name=".BaseActivity"
android:label="#string/title_activity_base" >
<intent-filter>
<action android:name="android.intent.action.SEARCH" />
</intent-filter>
<meta-data
android:name="android.app.searchable"
android:resource="#xml/searchable" />
</activity>
<activity
android:name=".UserActivity"
android:label="#string/title_activity_user" >
</activity>
<activity
android:name=".UserViewerActivity"
android:label="#string/title_activity_user_viewer" >
</activity>
</application>
</manifest>
There is no error in the LogCat and the onClick method is not caled.
I've tryed different methods of using the listener but never got any response. I also tryed a code that worked for me befor but no response.
Would be great if you culd help me out ;)

When using a DrawerLayout, there should be only one main content View, with the drawer View - in this case, your ListView - listed after it. Using a DrawerLayout in any other way will result in incorrect, unpredictable behavior, often preventing normal interaction with other layout elements.
A tutorial with links to a sample and docs can be found on this developer page.

Here I am giving an example of Image button. If it is also giving error then clean projects of eclipse and try again.
<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" >
<ImageButton
android:id="#+id/imageButton1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#+id/textView1"
android:layout_below="#+id/textView1"
android:layout_marginRight="35dp"
android:layout_marginTop="32dp"
android:contentDescription="image"
android:src="#drawable/ic_launcher" />
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageButton;
import android.widget.Toast;
public class MainActivity extends Activity {
ImageButton imgButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addListenerOnButton();
}
private void addListenerOnButton() {
imgButton = (ImageButton) findViewById(R.id.imageButton1);
imgButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(MainActivity.this, "Clicked", Toast.LENGTH_SHORT)
.show();
}
});
}
}

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.DisplayMessageActivity}

I’m following the android tutorial First App in the link below:
https://developer.android.com/training/basics/firstapp/starting-activity.html
The app can be launched in the emulator but the problem is when I click on the button “send, the application crashed with the message “unfortunately, my fist app has stopped”.
I think I did follow the instructions in the tutorial and can’t figure out where is the problem from.
Logcat send this message:
02-12 16:19:36.031: E/AndroidRuntime(786): java.lang.RuntimeException:
Unable to instantiate activity
ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.DisplayMessageActivity}:
java.lang.NullPointerException
activity_main.xml
<LinearLayout 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:orientation="horizontal">
<EditText android:id="#+id/edit_message"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="#string/edit_message" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send"
android:onClick="sendMessage" />
</LinearLayout>
MAinActivity.java
package com.example.myfirstapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
// Do something in response to button
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#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;
}
}
activity_display_message.xml
<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=".DisplayMessageActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
</RelativeLayout>
DisplayMessageActivity.java
package com.example.myfirstapp;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.view.MenuItem;
import android.widget.TextView;
public class DisplayMessageActivity extends Activity {
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
#SuppressLint("NewApi")
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Get the message from the intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
// Create the text view
TextView textView = new TextView(this);
textView.setTextSize(40);
textView.setText(message);
// Set the text view as the activity layout
setContentView(textView);
// Make sure we're running on Honeycomb or higher to use ActionBar APIs
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
// Show the Up button in the action bar.
getActionBar().setDisplayHomeAsUpEnabled(true);
}
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
}
MyFirstApp Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myfirstapp"
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.myfirstapp.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="com.example.myfirstapp.DisplayMessageActivity"
android:label="#string/title_activity_display_message"
android:parentActivityName="com.example.myfirstapp.MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.example.myfirstapp.MainActivity" />
</activity>
</application>
</manifest>
Thank you for your help

I believe the problem is
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
before onCreate(). Intent needs a Context which isn't available until the Activity has been created. Remove those lines since you already have it in onCreate().
Also, when it crashes, post your full logcat because it will tell us, usually, exactly where and what the problem is.

Button's don't work when clicked on, Code is correct

I tried test files like HelloWorld and Count Down timer. Neither of the buttons on my app seem to work. These segments of code are ones I downloaded from the internet, and they have been reported to work. I don't know what the issue could be. I am also very new eclipse and android app programming.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:textColor="#FF0000"
android:background="#000000"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#FF0000"
android:text="CountDown Timer Demo"
/>
<Button
android:text="Seizure Detected"
android:id="#+id/start"
android:textColor="#FF0000"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
<Button
android:text="Override"
android:id="#+id/stop"
android:textColor="#FF0000"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
<Button
android:text="click me"
android:id="#+id/Button01"
android:textColor="#FF0000"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</Button>
<TextView
android:id="#+id/tv"
android:textColor="#FF0000"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="sexy"/>
</LinearLayout>
CountDownTest.java >In the src folder
package com.example.epilepsytestapp;
import android.app.Activity;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class CountDownTest extends Activity {
Button start, stop;
TextView tv;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
start = (Button)this.findViewById(R.id.start);
stop = (Button)this.findViewById(R.id.stop);
tv = (TextView)this.findViewById(R.id.tv);
tv.setText("10"); // startting from 10.
final MyCounter timer = new MyCounter(10000,1000);
start.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
timer.start();
}
});
stop.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
timer.cancel();
}
});
}
public class MyCounter extends CountDownTimer{
public MyCounter(long millisInFuture, long countDownInterval) {
super(millisInFuture, countDownInterval);
}
#Override
public void onFinish() {
System.out.println("Timer Completed.");
tv.setText("Timer Completed.");
}
#Override
public void onTick(long millisUntilFinished) {
tv.setText((millisUntilFinished/1000)+"");
System.out.println("Timer : " + (millisUntilFinished/1000));
}
}
}
Here is Helloworld.java
package com.example.epilepsytestapp;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class HelloWorld extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = (Button) this.findViewById(R.id.Button01);
button.setOnClickListener(new OnClickListener() {
//#Override
public void onClick(View v) {
Toast.makeText(HelloWorld.this, "Hello World", Toast.LENGTH_SHORT).show();
}
});
}
}
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.epilepsytestapp"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity android:name=".CountDownTest"/>
<activity
android:name="com.example.epilepsytestapp.MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN"
android:name=".CountDownTest"/>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

try this.Your hello world code
package com.example.epilepsytestapp;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = (Button) findViewById(R.id.Button01);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(this, "Hello World", Toast.LENGTH_SHORT).show();
}
});
}
}

developer.android.com My First Android App | Stopped Error

i tried to run my first android application but i could not execute it. i followed instructions step by step from developer.android.com . I used only Copy and Paste for codes. But when i try to run my app AVD is giving error "Unfortunately, My First App has stooped."
Screen Captures are here :
AVD Settings : Click
LOG FILE:Click
AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myfirstapp"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<application
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="#string/title_activity_main" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".DisplayMessageActivity"
android:label="#string/title_activity_display_message" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.example.myfirstapp.MainActivity" />
</activity>
</application>
</manifest>
activity_main.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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<EditText android:id="#+id/edit_message"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="#string/edit_message"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send"
android:onClick="SendMessage"
/>
</LinearLayout>
activity_display_message.xml
<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" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="#string/hello_world"
tools:context=".DisplayMessageActivity" />
</RelativeLayout>
strings.xml
<resources>
<string name="app_name">My First App</string>
<string name="menu_settings">Settings</string>
<string name="title_activity_main">MainActivity</string>
<string name="edit_message">Bir şeyler yaz</string>
<string name="button_send">Send</string>
<string name="hello_world">Hello world!</string>
<string name="title_activity_display_message">My Message</string>
</resources>
DisplayMessageActivity.java
package com.example.myfirstapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.*;
public class DisplayMessageActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Get the message from the intent
Intent intent = getIntent();
String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
// Create the text view
TextView textView = new TextView(this);
textView.setTextSize(40);
textView.setText(message);
// Set the text view as the activity layout
setContentView(textView);
}
}
MainActivity.java
package com.example.myfirstapp;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.*;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
}
}

typo mistake in Button click method,s is not small its capital in xml layout file...
public void SendMessage(View view) {
^