java - 空对象引用上的 android.app.ActivityThread.getApplicationThread()'

Question

microhonePopUp 方法将在 MainActivity 中工作，但我希望它在另一个类 (MediaButtonIntentReceiver) 中工作。问题出在 startActivityForResult(intent, REQUEST_CODE); - 但我不知道如何解决它。

在MainActivity类中

public void microphonePopUp(){
        Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
        intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
                RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
        intent.putExtra(RecognizerIntent.EXTRA_PROMPT, "Voice your answer");
        startActivityForResult(intent, REQUEST_CODE);
    }

在 MediaButtonIntentReceiver 类中

public class MediaButtonIntentReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        if (Intent.ACTION_MEDIA_BUTTON.equals(intent.getAction())) {
            KeyEvent event = (KeyEvent)intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT);
            if (KeyEvent.KEYCODE_HEADSETHOOK == event.getKeyCode()) {
                MainActivity test = new MainActivity(); 
                test.microphonePopUp();
            }
        }
    }
}

12-09 11:20:14.803 19556-19556/com.timtennyson.priceaddition E/AndroidRuntime: FATAL EXCEPTION: main Process: com.timtennyson.priceaddition, PID: 19556 java.lang.RuntimeException: Unable to start receiver com.timtennyson.priceaddition.MediaButtonIntentReceiver: java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.ActivityThread$ApplicationThread android.app.ActivityThread.getApplicationThread()' on a null object reference at android.app.ActivityThread.handleReceiver(ActivityThread.java:3641) at android.app.ActivityThread.access$2000(ActivityThread.java:221) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1876) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:158) at android.app.ActivityThread.main(ActivityThread.java:7224) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.ActivityThread$ApplicationThread android.app.ActivityThread.getApplicationThread()' on a null object reference at android.app.Activity.startActivityForResult(Activity.java:4283) at android.app.Activity.startActivityForResult(Activity.java:4230) at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:842) at com.timtennyson.priceaddition.MainActivity.microphonePopUp(MainActivity.java:103) at com.timtennyson.priceaddition.MediaButtonIntentReceiver.onReceive(MediaButtonIntentReceiver.java:27) at android.app.ActivityThread.handleReceiver(ActivityThread.java:3634) at android.app.ActivityThread.access$2000(ActivityThread.java:221)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1876)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:158)  at android.app.ActivityThread.main(ActivityThread.java:7224)  at java.lang.reflect.Method.invoke(Native Method)

Answer 1

切勿自行创建 Activity 、服务或提供程序的实例。

如果您的目标是在 MainActivity 可见时监听 ACTION_MEDIA_BUTTON 广播:

• 将 MediaButtonIntentReceiver 移动为 MainActivity 内的嵌套类

• 从 onReceive() 中删除 test，只调用 microphonePopUp() (我认为这是一个方法) MainActivity)

• 使用 MainActivity 的 onStart() 中的 registerReceiver() 注册您的 MediaButtonIntentReceiver，然后使用onStop() 中的 unregisterReceiver()

如果您的目标是在其他时间点收听 ACTION_MEDIA_BUTTON 广播(通过在 list 中注册接收器)，虽然您可以做到这一点，但不能使用 microphonePopUp() 来自该接收器。