Question

在我的onCreate的{{1}}方法中，我按如下方式加载home片段：

main activity

旋转屏幕时，由于HomeFragment fragment = new HomeFragment().setData(data); // data is a List<XYZ> FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.bottom_navigation_frame, fragment); transaction.commit();为空，应用会以onCreateView的{{1}}方法崩溃。

我不确定何时应该保存和恢复HomeFragment的状态，data是从数据库加载的大对象。尝试保存时可能会收到另一个错误。那么如何旋转屏幕时应该解决空指针问题？

Answer 1

当配置更改或屏幕旋转时，片段丢失其数据。因此您必须在onPause上卸载片段，然后在屏幕更改配置时重新加载数据和片段。这是屏幕方向更改的监听器。

 m_sensorEventListener = new SensorEventListener() {
    @Override
    public void onSensorChanged(SensorEvent event) {
        if(getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {
            Log.i(TAG,"Orientation : PORTRAIT");
        }
        else {
            Log.i(TAG,"Orientation : LANDSCAPE");
        }
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {}
};

SensorManager sm = (SensorManager)getSystemService(SENSOR_SERVICE);
sm.registerListener(m_sensorEventListener, sm.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR), SensorManager.SENSOR_DELAY_NORMAL);

Answer 2

将此代码添加到Manifest.xml中的Current Activity的属性中

M =[(1, 1), (5, 6), (0, 0)]

1) print([any(x) for x in M])
[True, True, False] #only the last tuple does not have any true element

2) print([all(x) for x in M])
[True, True, False] #all elements of the last tuple are not true

3) print([not all(x) for x in M])
[False, False, True] #NOT operator applied to 2)

4) print([any(x)  and not all(x) for x in M])
[False, False, False] #AND operator applied to 1) and 3)
# if we had M =[(1, 1), (5, 6), (1, 0)], we could get [False, False, True]  in 4)
# because the last tuple satisfies both conditions: any of its elements is TRUE 
#and not all elements are TRUE

Android：片段导致屏幕旋转崩溃

2 个答案: