Android getBaseContext getApplicationContext不工作

Question

在为Android开发的Eclipse Java中······

Context c = getBaseContext();  // returns null
Context c = this.getBaseContext(); // throws an exception.

Context c = getApplicationContext();  // throws an exception
Context c = this.getApplicationContext();  // throws an exception.

File f = getFilesDir(); // throws an exception
File f = this.getFilesDir(); // throws an exception

正如您所看到的，我根本无法获得应用程序或基本上下文。试图在没有它们的情况下获得文件目录是行不通的。我到底如何访问我的文件目录？

public class SoundHandler extends Activity {
private Button mButtonPlay;
private Button mButtonDone;
// private LinearLayout mOverallView;
private PeekActivity mHome;
private MyButtonListener myButtonListener;
private MediaPlayer mPlayer; 
private File audioFilePath;

public SoundHandler(PeekActivity home) {
    mHome = home;
    myButtonListener = new MyButtonListener();
}

public void onCreate(Bundle savedInstanceState) {        
    super.onCreate(savedInstanceState);
}

public void open() {
    mHome.setContentView(R.layout.sounds);
    mButtonDone = (Button) mHome.findViewById(R.id.soundDone);     
    mButtonDone.setOnClickListener(myButtonListener);
    mButtonPlay = (Button) mHome.findViewById(R.id.playSound);     
    mButtonPlay.setOnClickListener(myButtonListener);
    mPlayer = null;

                // This is what I thought would work, but it does not
    audioFilePath = this.getBaseContext().getFilesDir().getAbsolutePath();  

                // These are my attempts to see what, if anything works and is not null
                // but I've tried all the combinations and permutations above.
    SoundHandler a = this;
    Context b = getBaseContext();
    Context c = getApplicationContext();
    File d = this.getFilesDir();

                // I'm really just trying to get access to an audio file that is included
                // in my build in file /res/raw/my_audio_file.mp3
                // mPlayer = MediaPlayer.create(this, R.raw.my_audio_file); doesn't work either
}

Answer 1

您很可能是在自己实例化活动或服务，或者BroadcastReceiver。如果是这种情况，请知道这些是Android可管理的对象，除了单元测试之外，您不能实例化它们。Android系统将负责根据所提供的意图实例化它们。所以不要调用它们的构造函数，它可能看起来“有效”，但它会显示出奇怪的副作用，就像你正在经历的这些一样。