在做相机开发时,遇到一个问题,就是需要监听屏幕旋转。最简单的就是使用onConfigurationChanged()和OrientationEventListener这两种方法来实现,但是最后都遇到了问题。
#1 一开始是使用onConfigurationChanged()这个回调,重新Activity里面的这个方法就可以了,简单又方便。用了之后发现,它只能监听,横屏切竖屏的情况。左横屏切右横屏是监听不到的,而且切完之后你也不知道是左横屏还是右横屏。下面是使用onConfigurationChanged()进行监听的简单使用。
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
if(newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE){
// 横屏
}else if(newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
// 竖屏
}
}
#2 之后又想到了OrientationEventListener来监听屏幕旋转的实时角度,这个非常灵活,手机转动实时角度都会回调出来。下面是使用OrientationEventListener的简单实现。在适当的位置调用enable()和disable()来开启和关闭监听。
class MyOrientationEventListener extends OrientationEventListener {
private static final int SENSOR_ANGLE = 10;
public MyOrientationEventListener(Context context) {
super(context);
}
@Override
public void onOrientationChanged(int orientation) {
Log.d(TAG, "onOrientationChanged orientation=" + orientation);
if (orientation == OrientationEventListener.ORIENTATION_UNKNOWN) {
return; //手机平放时,检测不到有效的角度
}
//下面是手机旋转准确角度与四个方向角度(0 90 180 270)的转换
if (orientation > 360 - SENSOR_ANGLE || orientation < SENSOR_ANGLE) {
orientation = 0;
} else if (orientation > 90 - SENSOR_ANGLE && orientation < 90 + SENSOR_ANGLE) {
orientation = 90;
} else if (orientation > 180 - SENSOR_ANGLE && orientation < 180 + SENSOR_ANGLE) {
orientation = 180;
} else if (orientation > 270 - SENSOR_ANGLE && orientation < 270 + SENSOR_ANGLE) {
orientation = 270;
} else {
return;
}
}
}
MyOrientationEventListener listener = new MyOrientationEventListener(this);
listener.enable();
listener.disable();
但是,它只有当手机竖直握持,然后左右转动时是有效的,手机平放,左右转动,是感应不到角度变化的。原因是OrientationEventListener原理是只采集了Sensor X和Y方向上的加速度进行计算的。可以从下面源码中看到orientation的值只跟X和Y有关。(下面的源码取自android.view.OrientationEventListener)而且使用这个判断还有一个弊端,就是当屏幕实际已经进行旋转切换,但是OrientationEventListener回调的值还没到达旋转后的值。这就导致了系统屏幕旋转了,但是我们app的UI因为没有收到callback而没有改变的问题。
class SensorEventListenerImpl implements SensorEventListener {
private static final int _DATA_X = 0;
private static final int _DATA_Y = 1;
private static final int _DATA_Z = 2;
public void onSensorChanged(SensorEvent event) {
float[] values = event.values;
int orientation = ORIENTATION_UNKNOWN;
float X = -values[_DATA_X];
float Y = -values[_DATA_Y];
float Z = -values[_DATA_Z];
float magnitude = X*X + Y*Y;
// Don't trust the angle if the magnitude is small compared to the y value
if (magnitude * 4 >= Z*Z) {
float OneEightyOverPi = 57.29577957855f;
float angle = (float)Math.atan2(-Y, X) * OneEightyOverPi;
orientation = 90 - (int)Math.round(angle);
// normalize to 0 - 359 range
while (orientation >= 360) {
orientation -= 360;
}
while (orientation < 0) {
orientation += 360;
}
}
if (mOldListener != null) {
mOldListener.onSensorChanged(Sensor.TYPE_ACCELEROMETER, event.values);
}
if (orientation != mOrientation) {
mOrientation = orientation;
onOrientationChanged(orientation);
}
}
#3 为了解决上述问题,其实最好的就是在系统屏幕旋转的时候,能有个回调,告诉我当前是哪个角度,这样就是最准确的了。但是onConfigurationChanged只能告诉你是横的还是竖的,虽然它做不了,但是给了一个方向。就是屏幕旋转系统调用onConfigurationChanged的时候,肯定是知道旋转后的角度的。根据阅读源码可知,当屏幕旋转时,会调用IRotationWatcher#onRotationChanged(),但是对app来说是Hide的api,无法对他进行监听。然后又发现android.hardware.LegacySensorManager类它在构造函数里面,对IRotationWatcher进行了注册,onRotationChanged()返回的值,也会保存在sRotation,所以可以在这里做文章了。
public class ScreenOrientationListener extends OrientationEventListener {
private static final String TAG = ScreenOrientationListener.class.getSimpleName();
private int mOrientation;
private OnOrientationChangedListener mOnOrientationChangedListener;
private Context mContext;
private Field mFieldRotation;
private Object mOLegacy;
public ScreenOrientationListener(Context context) {
super(context);
mContext = context;
}
public void setOnOrientationChangedListener(OnOrientationChangedListener listener) {
this.mOnOrientationChangedListener = listener;
}
public int getOrientation() {
int rotation = -1;
try {
if (null == mFieldRotation) {
SensorManager sensorManager = (SensorManager) mContext.getSystemService(Context.SENSOR_SERVICE);
Class clazzLegacy = Class.forName("android.hardware.LegacySensorManager");
Constructor constructor = clazzLegacy.getConstructor(SensorManager.class);
constructor.setAccessible(true);
mOLegacy = constructor.newInstance(sensorManager);
mFieldRotation = clazzLegacy.getDeclaredField("sRotation");
mFieldRotation.setAccessible(true);
}
rotation = mFieldRotation.getInt(mOLegacy);
} catch (Exception e) {
Log.e(TAG, "getRotation e=" + e.getMessage());
e.printStackTrace();
}
// Log.d(TAG, "getRotation rotation=" + rotation);
int orientation = -1;
switch (rotation) {
case Surface.ROTATION_0:
orientation = 0;
break;
case Surface.ROTATION_90:
orientation = 90;
break;
case Surface.ROTATION_180:
orientation = 180;
break;
case Surface.ROTATION_270:
orientation = 270;
break;
default:
break;
}
// Log.d(TAG, "getRotation orientation=" + orientation);
return orientation;
}
@Override
public void onOrientationChanged(int orientation) {
if (orientation == OrientationEventListener.ORIENTATION_UNKNOWN) {
return; // 手机平放时,检测不到有效的角度
}
orientation = getOrientation();
if (mOrientation != orientation) {
mOrientation = orientation;
if (null != mOnOrientationChangedListener) {
mOnOrientationChangedListener.onOrientationChanged(mOrientation);
Log.d(TAG, "ScreenOrientationListener onOrientationChanged orientation=" + mOrientation);
}
}
}
public interface OnOrientationChangedListener {
void onOrientationChanged(int orientation);
}
}
上面的代码,就是通过监听OrientationEventListener实时角度变化,然后使用反射的方法去获取LegacySensorManager里面的rotation,这样拿到的角度就是准确的,在配合角度变化时才回调callback,就完美实现了4个方向角度旋转时的监听。