android 传感器获取方向总结

在2.2中可以设置屏幕的方向为反转横屏:setRequestedOrientation(8);，因为系统没有公开出这个参数的设置，不过在源码里面已经定义了SCREEN_ORIENTATION_REVERSE_LANDSCAPE这个参数，但是无法固定屏幕的方向为反转横屏即右横屏。在设置屏幕方向为右横屏的时候还得注意一点，需要将activity设置为android:theme="@android:style/Theme.Translucent",否则即使设置了setRequestedOrientation(8);也不会显示为右横屏。

虽然能根据旋转角度获取到屏幕的方向，但是在2.1的时候根本无法设置为右横屏，下面记录一点从源码抠出来的根据传感器根据角度获取屏幕方向。

传感器监听：

class SubSensorListener implements SensorEventListener {private static final int _DATA_X = 0;private static final int _DATA_Y = 1;private static final int _DATA_Z = 2;public static final int ORIENTATION_UNKNOWN = -1;private Handler handler;public SubSensorListener (Handler handler) {this.handler = handler;}public void onAccuracyChanged(Sensor arg0, int arg1) {}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 valueif (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 rangewhile (orientation >= 360) {orientation -= 360;}while (orientation < 0) {orientation += 360;}}if (handler != null) {handler.obtainMessage(123, orientation, 0).sendToTarget();}}

由于方向的改变会不断发生变化，所以我们需要一个handler来处理，下面是handler通过对旋转角度的处理获得方向：

@Overridepublic void handleMessage(Message msg) {if (msg.what == 123) {int orientation = msg.arg1;if (orientation > 45 && orientation < 135) {// SCREEN_ORIENTATION_REVERSE_LANDSCAPEactivity.setRequestedOrientation(8);} else if (orientation > 135 && orientation < 225) {// SCREEN_ORIENTATION_REVERSE_PORTRAITactivity.setRequestedOrientation(9);} else if (orientation > 225 && orientation < 315) {// SCREEN_ORIENTATION_LANDSCAPEactivity.setRequestedOrientation(0);} else if ((orientation > 315 && orientation < 360) || (orientation > 0 && orientation < 45)) {// SCREEN_ORIENTATION_PORTRAITactivity.setRequestedOrientation(1);}}}

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