不幸的是，当应用程序在genymotion模拟器上运行时，android已经停止工作

Question

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);
    } }

<?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：无法执行Android的方法:onclick
在Android.support.v7.app.appcompatviewWinflater$declaredonClickListener.onclick(appcompatviewWinflater$declaredonClickListener.android.view.view.view.performClick(View.java:275)在Android.view.view.view.view.performClick(View.java:4438)在Android.view.view read.main（activitythread.java：5001）在java.lang.reflect.method.invokenative（原生方法）在java.lang.reflect.method.invoke（method.java：515）在com.android.internal.os.zygoteinit$methodandArgsCaller.run（zygoteinit.java：785)在com.android.internal.os.zygoteinit.main（原生方法）在dalvik.system.nativeStart.main（原生方法）在在Android.support.v处调用(method.java:515)7.app.appcompatviewinflater$declaredonclicklistener.onclick(appcompatviewwinflater.java:270)在Android.view.view.performclick(View.java:4438) 在Android.view.view$performclick.run（view.java:18422) 在Android.os.handler.handleCallback（handler.java:733) 在Android.os.handler.DispatchMessage(Handler.java:95) 在Android.os.looper.loop(looper.java:136)， 在Android.app.activitythread.main(activitythread.java:5001) 在java.lang.reflect.Method.invokenative（本机方法） 在java.lang.reflect.method.invoke(Method.java:515) 在com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:785) 在com.android.internal.os.zygoteinit.main(zygoteinit.java:601) 在dalvik.system.nativeStart.main（原生方法） 由：java.lang.NullPointerException在toast.akappstudio.com.audiodemo.mainActivity.PlayAudio（mainActivity.java:17)在java.lang.reflect.Method.Invokenative（本机方法） 在java.lang.reflect.method.invoke(Method.java:515) 在Android.support.v7.app.appCompatviewInflater$DeclaredonClickListener.onClick(AppCompatviewWinflater.html" target="_blank">java:270) 在Android.view.view.performClick（view.java：4438） 在Android.view.view$performclick.run（view.java:18422) 在Android.os.handler.handleCallback（handler.java:733) 在Android.os.handler.DispatchMessage(Handler.java:95) 在Android.os.looper.loop(looper.java:136)， 在Android.app.activitythread.main(activitythread.java:5001) 在java.lang.reflect.Method.invokenative（本机方法） 在java.lang.reflect.method.invoke(Method.java:515) 在com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:785) 在com.android.internal.os.zygoteinit.main(zygoteinit.java:601) 在dalvik.system.nativeStart.main（原生方法） 06-28 13:40:39.326 247 7-2477/？I/process：发送信号。PID：2477签名：9

Answer 1

改变

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

到

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

在oncreate()方法中。