Question

This activity is supposed to call another activity, but instead it force closes the application.

package com.example.helloworld;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Data extends Activity implements OnClickListener {

    Button start, startFor;
    EditText sendET;
    TextView gotAnswer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.get);
        initialize();
    }

    private void initialize() {
        // TODO Auto-generated method stub
        start = (Button) findViewById(R.id.bSA);
        startFor = (Button) findViewById(R.id.bSAFR);
        sendET = (EditText) findViewById(R.id.etSend);
        gotAnswer = (TextView) findViewById(R.id.tvGot);
        start.setOnClickListener(this);
        startFor.setOnClickListener(this);
    }

    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch (v.getId()) {
        case R.id.bSA:
            String bread = sendET.getText().toString();
            Bundle basket = new Bundle();
            basket.putString("key", bread);

            Intent a = new Intent(Data.this, OpenedClass.class);
            a.putExtras(basket); 
            startActivity(a);
            break;

        case R.id.bSAFR:
            Intent i = new Intent(Data.this, OpenedClass.class);
            startActivityForResult(i,0);
            break;
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        super.onActivityResult(requestCode, resultCode, data);
    }

}

This is the other Activity that is to be called:

package com.example.helloworld;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TextView;

public class OpenedClass extends Activity implements OnClickListener,
        OnCheckedChangeListener {

    TextView question, test;
    Button returnData;
    RadioGroup selectionList;
    String gotBread, setData;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.send);
        initialize();
        Bundle gotBasket = getIntent().getExtras();
        gotBread = gotBasket.getString("key");
        question.setText(gotBread);

    }

    private void initialize() {
        // TODO Auto-generated method stub
        question = (TextView) findViewById(R.id.tvQuestions);
        test = (TextView) findViewById(R.id.tvText);
        returnData = (Button) findViewById(R.id.bResults);
        selectionList = (RadioGroup) findViewById(R.id.rgAnswers);
        returnData.setOnClickListener(this);
        selectionList.setOnCheckedChangeListener(this);


    }

    public void onClick(View v) {
        // TODO Auto-generated method stub

    }

    public void onCheckedChanged(RadioGroup arg0, int arg1) {
        // TODO Auto-generated method stub
        switch (arg1) {
        case R.id.rChoice1:
            setData="ABC";
            break;
        case R.id.rChoice2:
            setData="MNO";
            break;
        case R.id.rChoice3:
            setData="XYZ";
            break;
        }
        test.setText(setData);
    }

}

This is my AndroidMaifest.xml file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.helloworld"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="15" />
    <uses-permission android:name="android.permission.SET_WALLPAPER"/>

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".Splash"
            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=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>

            </intent-filter>
        </activity>
        <activity
            android:name=".Menu"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="com.example.helloworld.MENU" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".TextPlay" android:label="@string/title_activity_main" >
        </activity>
         <activity
            android:name=".Email" android:label="@string/title_activity_main" >
        </activity>
        <activity
            android:name=".Camera" android:label="@string/title_activity_main" android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Data" android:label="@string/title_activity_main" >
        </activity>
        <activity
            android:name=".OpenedClass" android:label="@string/title_activity_main" >
        </activity>
    </application>

</manifest>

Finally the LogCat logs:

10-17 10:36:56.423: D/AndroidRuntime(272): Shutting down VM
10-17 10:36:56.423: W/dalvikvm(272): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
10-17 10:36:56.453: E/AndroidRuntime(272): FATAL EXCEPTION: main
10-17 10:36:56.453: E/AndroidRuntime(272): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.helloworld/com.example.helloworld.OpenedClass}: java.lang.NullPointerException
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.os.Looper.loop(Looper.java:123)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.ActivityThread.main(ActivityThread.java:4627)
10-17 10:36:56.453: E/AndroidRuntime(272):  at java.lang.reflect.Method.invokeNative(Native Method)
10-17 10:36:56.453: E/AndroidRuntime(272):  at java.lang.reflect.Method.invoke(Method.java:521)
10-17 10:36:56.453: E/AndroidRuntime(272):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-17 10:36:56.453: E/AndroidRuntime(272):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-17 10:36:56.453: E/AndroidRuntime(272):  at dalvik.system.NativeStart.main(Native Method)
10-17 10:36:56.453: E/AndroidRuntime(272): Caused by: java.lang.NullPointerException
10-17 10:36:56.453: E/AndroidRuntime(272):  at com.example.helloworld.OpenedClass.initialize(OpenedClass.java:38)
10-17 10:36:56.453: E/AndroidRuntime(272):  at com.example.helloworld.OpenedClass.onCreate(OpenedClass.java:25)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-17 10:36:56.453: E/AndroidRuntime(272):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-17 10:36:56.453: E/AndroidRuntime(272):  ... 11 more
10-17 10:36:59.083: I/Process(272): Sending signal. PID: 272 SIG: 9

The problem is that the application compiles without errors but crashes when I try to invoke the activity. I’m not sure where the problem is. Is it the manifest?

Answer 1

If I counted lines correctly (to line 38 of OpenedClass.java) the NPE is being generated at this line:

returnData.setOnClickListener(this);

inside OpenedClass.initialize(). The variable returnData is being initialize a couple of lines above by:

returnData = (Button) findViewById(R.id.bResults);

The problem is most likely that your layout (send.xml) does not have a bResults view so returnData is being assigned null.