getApplicationContext() 不适用于为 JobService

Question

我正在使用JobSchedulerwhichAsyncTask用于其JobService. 在MJobExecutor扩展AsyncTask使用MediaPlayer哪个需要getApplicationContext()作为参数的类中不起作用。它显示无法解析方法。public class MJobExecutor extends AsyncTask<Void,Void,String> {ValueExchange value;MediaPlayer player;@Overrideprotected String doInBackground(Void... params) {    value = new ValueExchange();    Calendar cal = Calendar.getInstance();    Date date=cal.getTime();    DateFormat dateFormat = new SimpleDateFormat("hh:mm a");    String formattedDate=dateFormat.format(date);    if(formattedDate.equals(value.getString())){    }    return "Long running task finishes." + value.getString();}private void play(){    if(player == null){        player = MediaPlayer.create(getApplicationContext(),R.raw.bensoundfunkyelement);        //In the above code getApplicationContext() not working-        //Cannot resolve method getApplicationContext()        //i have used this as context not working.        //getBaseActivity() not working.        //getActivity().getApplicationContext() also not working.      player.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {            @Override            public void onCompletion(MediaPlayer mp) {                stopPlayer();            }        });    }    player.start();}private void stop(){    stopPlayer();}private void stopPlayer(){    if(player != null){        player.release();        player = null;    }}}

Answer 1

您不能getApplicationContext()从 an 内部调用，AsyncTask因为该方法是在Contextclass 而不是在 class 中定义的AsyncTask。仅供参考，您可以在Activity或Service或其子类中使用此方法，因为这些类是Context.

为了解决您的问题，您需要通过构造函数或 setter传递一个Context对象或一个MediaPlayer对象AsyncTask。

例如：

public class YourTask extends AsyncTask<Void, Void, String> {

    private MediaPlayer player;

    public YourTask(MediaPlayer player) {

        this.player = player;

    }

    @Override

    protected String doInBackground(Void... voids) {

        // todo

        return null;

    }

}