Unfortunately android has stopped working when the app is run on genymotion emulator

Question

I tried to make a very simple audio player but later when the app was run on the emulator, on clicking the play button it popped up the error "Unfortunately android has stopped working" and it crashed.

This is my code.

MainActivity.java

package toast.akappstudio.com.audiodemo;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    MediaPlayer player;

    public void playAudio(View view){


        player.start();

    }
    public void pauseAudio(View view){

        player.pause();
    }

    public void stopAudio(View view){

        player.stop();
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MediaPlayer player = MediaPlayer.create(this, R.raw.audio);
    }

    @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_main, 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);
    } }

content.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="toast.akappstudio.com.audiodemo.MainActivity"
    tools:showIn="@layout/activity_main">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Play"
        android:id="@+id/playbutton"
        android:layout_marginLeft="67dp"
        android:layout_marginStart="67dp"
        android:layout_marginTop="176dp"
        android:onClick="playAudio"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Pause"
        android:id="@+id/pausebutton"
        android:layout_marginLeft="55dp"
        android:layout_marginStart="55dp"
        android:onClick="pauseAudio"
        android:layout_alignTop="@+id/playbutton"
        android:layout_toRightOf="@+id/playbutton"
        android:layout_toEndOf="@+id/playbutton" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="STOP"
        android:id="@+id/stopbutton"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:onClick="stopAudio" />
</RelativeLayout>

LOGCAT:

java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:275) at android.view.View.performClick(View.java:4438) at android.view.View$PerformClick.run(View.java:18422) at android.os.Handler.handleCallback(Handler.java:733) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5001) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.reflect.InvocationTargetException at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270) at android.view.View.performClick(View.java:4438)  at android.view.View$PerformClick.run(View.java:18422)  at android.os.Handler.handleCallback(Handler.java:733)  at android.os.Handler.dispatchMessage(Handler.java:95)  at android.os.Looper.loop(Looper.java:136)  at android.app.ActivityThread.main(ActivityThread.java:5001)  at java.lang.reflect.Method.invokeNative(Native Method)  at java.lang.reflect.Method.invoke(Method.java:515)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)  at dalvik.system.NativeStart.main(Native Method)  Caused by: java.lang.NullPointerException at toast.akappstudio.com.audiodemo.MainActivity.playAudio(MainActivity.java:17) at java.lang.reflect.Method.invokeNative(Native Method)  at java.lang.reflect.Method.invoke(Method.java:515)  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270)  at android.view.View.performClick(View.java:4438)  at android.view.View$PerformClick.run(View.java:18422)  at android.os.Handler.handleCallback(Handler.java:733)  at android.os.Handler.dispatchMessage(Handler.java:95)  at android.os.Looper.loop(Looper.java:136)  at android.app.ActivityThread.main(ActivityThread.java:5001)  at java.lang.reflect.Method.invokeNative(Native Method)  at java.lang.reflect.Method.invoke(Method.java:515)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)  at dalvik.system.NativeStart.main(Native Method)  06-28 13:40:39.326 2477-2477/? I/Process: Sending signal. PID: 2477 SIG: 9

Answer 1

Change

`MediaPlayer player = MediaPlayer.create(this, R.raw.audio);`

to

`player = MediaPlayer.create(this, R.raw.audio);` 

in your onCreate() method.

Reason

You are creating a global variable mediaPlayer and you're also declaring another variable in onCreate() of the same name. The one inside the onCreate() will become a local variable instance and since you're not initializing your global variable it will be null. So when you were trying to access it in your play(), pause() and stop() you will get null pointer exception. Hope my explanation gave you clarity :)