Question

I know there are many people who have the problem. I’ve tried many ways I can find, however still get the error.

1. there’s only one activity and it’s registered.
2. tried to complete .MainActivity by com.hermione.woodenfish.MainActivity, no use
3. clean and rebuild don’t work either

really need help, thanks!!

LogCat:

08-01 12:09:33.944: E/Trace(1032): error opening trace file: No such file or directory (2)
08-01 12:09:34.384: D/AndroidRuntime(1032): Shutting down VM
08-01 12:09:34.424: W/dalvikvm(1032): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
08-01 12:09:34.465: E/AndroidRuntime(1032): FATAL EXCEPTION: main
08-01 12:09:34.465: E/AndroidRuntime(1032): java.lang.RuntimeException: Unable to     instantiate activity   ComponentInfo{com.hermione.woodenfish/com.hermione.woodenfish.MainActivity}: java.lang.NullPointerException
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.os.Looper.loop(Looper.java:137)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.ActivityThread.main(ActivityThread.java:4745)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at java.lang.reflect.Method.invokeNative(Native Method)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at java.lang.reflect.Method.invoke(Method.java:511)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at dalvik.system.NativeStart.main(Native Method)
08-01 12:09:34.465: E/AndroidRuntime(1032): Caused by: java.lang.NullPointerException
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.content.ContextWrapper.getResources(ContextWrapper.java:81)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.media.MediaPlayer.create(MediaPlayer.java:824)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at com.hermione.woodenfish.MainActivity.<init>(MainActivity.java:24)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at java.lang.Class.newInstanceImpl(Native Method)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at java.lang.Class.newInstance(Class.java:1319)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
08-01 12:09:34.465: E/AndroidRuntime(1032):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
08-01 12:09:34.465: E/AndroidRuntime(1032):     ... 11 more
08-01 12:33:02.784: E/Trace(1171): error opening trace file: No such file or directory (2)
08-01 12:33:03.125: D/AndroidRuntime(1171): Shutting down VM
08-01 12:33:03.125: W/dalvikvm(1171): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
08-01 12:33:03.154: E/AndroidRuntime(1171): FATAL EXCEPTION: main
08-01 12:33:03.154: E/AndroidRuntime(1171): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.hermione.woodenfish/com.hermione.woodenfish.MainActivity}: java.lang.NullPointerException
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.os.Looper.loop(Looper.java:137)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.ActivityThread.main(ActivityThread.java:4745)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at java.lang.reflect.Method.invokeNative(Native Method)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at java.lang.reflect.Method.invoke(Method.java:511)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at dalvik.system.NativeStart.main(Native Method)
08-01 12:33:03.154: E/AndroidRuntime(1171): Caused by: java.lang.NullPointerException
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.content.ContextWrapper.getResources(ContextWrapper.java:81)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.media.MediaPlayer.create(MediaPlayer.java:824)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at com.hermione.woodenfish.MainActivity.<init>(MainActivity.java:23)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at java.lang.Class.newInstanceImpl(Native Method)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at java.lang.Class.newInstance(Class.java:1319)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
08-01 12:33:03.154: E/AndroidRuntime(1171):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
08-01 12:33:03.154: E/AndroidRuntime(1171):     ... 11 more

MainActivity.java

package com.hermione.woodenfish;

import android.app.Activity;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

    @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;
    }

    private MediaPlayer mp = MediaPlayer.create(this, R.raw.knok);
    public void sendKnok(View view) {
        if (mp.isPlaying()){
            mp.stop();
        }
        mp.start();
    }
}

Manifest:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hermione.woodenfish"
    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>
    </application>

</manifest>

Answer 1

I think the problem is here in this line,

 private MediaPlayer mp = MediaPlayer.create(this, R.raw.knok);

You have tried to initialize the Context object before the onCreate(). This might be creating the problem. How about you Initialize your MediaPlayer inside your onCreate(),

private MediaPlayer mp =null;  //Global Declaration

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    mp = MediaPlayer.create(this, R.raw.knok);
}