java - onStop Error, app shuts down

Question

I am trying to stop a melody from playing when user hit the back-button. This code is working when the file is playing, if not there will be an error and the app shuts down. How come it isnt working?

MediaPlayer melodisnutt;
public void onStop() {
    super.onStop();
    if ( melodisnutt.isPlaying () ) {
        melodisnutt.stop();
    }
}

Answer 1

如果您确定错误发生在 onStop() 方法中，则它看起来像一个 nullPointerException。

尝试更换：

if(melodisnutt.isPlaying()){

经过

if(melodisnutt != null && melodisnutt.isPlaying()){

Answer 2

最好检查您的 MediaPlayer 是否不为空，

public void onStop() {
    super.onStop();
    if (melodisnutt.isPlaying () && melodisnutt != null) {
        melodisnutt.stop();
    }
}