小编Err*_*ror的帖子

用Logclass跟踪运行时显示onReceive()方法没有调用,为什么？

动态注册广播接收器

 private void discoverDevices () {
    Log.e("MOHAB","BEFORE ON RECEIVE");

     mReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
            Log.e("MOHAB","ON RECEIVE");
            String action = intent.getAction();
            // When discovery finds a device
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                // Get the BluetoothDevice object from the Intent
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                // Add the name and address to an array adapter to show in a ListView
                Bluetooth b = new Bluetooth(device.getName(),device.getAddress());
                list.add(b);
            }
        }
    };
    Log.e("MOHAB","create intentFilter");
    // …

我LinearLayout在屏幕旋转后返回对象返回的nullPointerException异常, 虽然我在onCreate()super.onCreate(null)中传递null ; .我知道Activity必须被销毁并重新创建旁边我传递的savedInstanceState = null表示Activity应该在旋转后开始,因为它是第一次启动,为什么我在轮换后得到这个Exception？

onCreate()片段,其中LinearLayout对象名为historyText

LinearLayout historyText ;  // this return exception if it used after rotation . 

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(null);
    setContentView(R.layout.activity_main);
    historyText = (LinearLayout) findViewById(R.id.historyLayoutText); 
    Log.e("HISTORYVISIBILITY", "VISIBILITY = "+historyText.getVisibility());
    getWindow().getDecorView().setSystemUiVisibility(
            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                    | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
    database = new Database(this);
    Bundle extras = getIntent().getExtras();
    intent = extras.getInt("activity");
    p = new Progress();
    getSupportFragmentManager().beginTransaction()
                .add(R.id.group, p)
                .commit();
    orientation = getRotation();
    switch (orientation){
        case "p" :
            addPlus();
    }
}

logcat的

    10-07 22:21:24.365: E/AndroidRuntime(7768): …