Question

我一直关注网络上的一些Android教程。我尝试尽最大努力复制他的代码，但每当我运行应用程序时它就会崩溃。我查看了控制台，发现它是一个导致它的Nullpointer异常。该应用程序旨在播放声音，然后关闭，然后转到另一个布局。这是我的代码，请告诉我我做错了什么。

    package com.greg.hello;

    import android.app.Activity;
    import android.content.Intent;
    import android.media.MediaPlayer;
    import android.os.Bundle;

    public class MainActivity extends Activity {
    MediaPlayer mpSplash;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.splash);
        MediaPlayer mpSplash = MediaPlayer.create(this, R.raw.explosion);
        mpSplash.start();
        Thread logoTimer = new Thread(){
            public void run(){
                try{
                    int logoTimer=0;
                    while(logoTimer<8000){
                        sleep(100);
                        logoTimer=logoTimer+100;
                    }
                    startActivity(new     Intent("com.greg.hello.CLEARSCREEN"));
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    setContentView(R.layout.tutorial1);
                    e.printStackTrace();
                }

                finally{
                    finish();
                }
            }   
        };
        logoTimer.start();
        finish();
    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        mpSplash.release();
        startActivity(new Intent("com.greg.hello.TUTORIALONE"));
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        mpSplash.pause();
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        mpSplash.start();
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onStop() {
        // TODO Auto-generated method stub
        super.onStop();
        setContentView(R.layout.activity_main);
    }

}

Answer 1

这绝对是一个NPE，替换

MediaPlayer mpSplash = MediaPlayer.create(this, R.raw.explosion);

与

this.mpSplash = MediaPlayer.create(this, R.raw.explosion);

Answer 2

内的onCreate()

MediaPlayer mpSplash = MediaPlayer.create(this, R.raw.explosion);

是一个局部变量。

替换为

this.mpSplash = MediaPlayer.create(this, R.raw.explosion);

发生NullPointerException时

* 。

onDestroy()

中的

您致电

mpSlash.release()

尚未初始化，但您认为它已在onCreate()

中初始化

Nullpointer例外

2 个答案: