利用GSensor让屏幕实现360度旋转

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我是靠谱客的博主愤怒学姐，最近开发中收集的这篇文章主要介绍利用GSensor让屏幕实现360度旋转，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

在 Android的 Settings->Sound and Display中有 Orientation这一设置项。当选中时，反转手机，手机屏幕会随之旋转，一般只可以旋转90度。

这一 settings设置是在文件 SoundAndDisplaySettings.java中，该项对应的键字符串为：

private static final String KEY_ACCELEROMETER = "accelerometer" ;

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Java代码

private static final String KEY_ACCELEROMETER = "accelerometer";

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其默认值保存在 xml文件中，默认是 Enable。 UI程序初始化时会根据其值是否在复选框中打勾（代码在 onCreate函数中）：

protected void onCreate(Bundle savedInstanceState) {
…
mAccelerometer = (CheckBoxPreference) findPreference(KEY_ACCELEROMETER);
mAccelerometer.setPersistent(false );
…
}

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Java代码

protected void onCreate(Bundle savedInstanceState) {
…
mAccelerometer = (CheckBoxPreference) findPreference(KEY_ACCELEROMETER);
mAccelerometer.setPersistent(false);
…
}

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当用户改变了该值时，会保存起来：

Java代码

public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
…
} else if (preference == mAccelerometer) {
Settings.System.putInt(getContentResolver(),
Settings.System.ACCELEROMETER_ROTATION,
mAccelerometer.isChecked() ? 1 : 0 );
…
}

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public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
…
} else if (preference == mAccelerometer) {
Settings.System.putInt(getContentResolver(),
Settings.System.ACCELEROMETER_ROTATION,
mAccelerometer.isChecked() ? 1 : 0);
…
}

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文件 frameworks/policies/base/phone/com/android/internal/policy/impl/PhoneWindowManager.java中的 SettingsServer会随时监控其值，对用户设置做出反应：

public void update() {
ContentResolver resolver = mContext.getContentResolver();
boolean updateRotation = false ;
synchronized (mLock) {
…
int accelerometerDefault = Settings.System.getInt(resolver,
Settings.System.ACCELEROMETER_ROTATION, DEFAULT_ACCELEROMETER_ROTATION);
if (mAccelerometerDefault != accelerometerDefault) {
mAccelerometerDefault = accelerometerDefault;
updateOrientationListenerLp();
}
…
}

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Java代码

publicvoid update() {
ContentResolver resolver = mContext.getContentResolver();
boolean updateRotation = false;
synchronized (mLock) {
…
int accelerometerDefault = Settings.System.getInt(resolver,
Settings.System.ACCELEROMETER_ROTATION, DEFAULT_ACCELEROMETER_ROTATION);
if (mAccelerometerDefault != accelerometerDefault) {
mAccelerometerDefault = accelerometerDefault;
updateOrientationListenerLp();
}
…
}

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上述是设置生效流程。当 Orientation设置 Enable时，会发生什么呢？

在 PhoneWindowManager.java有个 Listener，它会根据 Sensor判别出的旋转方向，调用 WindowManager.setRotation让屏幕进行旋转。另外，当应用程序显示禁止屏幕旋转时则不会旋转，见函数 needSensorRunningLp()。

class MyOrientationListener extends WindowOrientationListener {
MyOrientationListener(Context context) {
super (context);
}
@Override
public void onOrientationChanged( int rotation) {
// Send updates based on orientation value
if ( true ) Log.i(TAG, "onOrientationChanged, rotation changed to " +rotation);
try {
mWindowManager.setRotation(rotation, false ,
mFancyRotationAnimation);
} catch (RemoteException e) {
// Ignore
}
}
}
MyOrientationListener mOrientationListener;
boolean useSensorForOrientationLp( int appOrientation) {
if (appOrientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR) {
return true ;
}
if (mAccelerometerDefault != 0 && (
appOrientation == ActivityInfo.SCREEN_ORIENTATION_USER ||
appOrientation == ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED)) {
return true ;
}
return false ;
}
/*
* We always let the sensor be switched on by default except when
* the user has explicitly disabled sensor based rotation or when the
* screen is switched off.
*/
boolean needSensorRunningLp() {
if (mCurrentAppOrientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR) {
// If the application has explicitly requested to follow the
// orientation, then we need to turn the sensor or.
return true ;
}
if (mAccelerometerDefault == 0 ) {
// If the setting for using the sensor by default is enabled, then
// we will always leave it on. Note that the user could go to
// a window that forces an orientation that does not use the
// sensor and in theory we could turn it off... however, when next
// turning it on we won't have a good value for the current
// orientation for a little bit, which can cause orientation
// changes to lag, so we'd like to keep it always on. (It will
// still be turned off when the screen is off.)
return false ;
}
return true ;
}

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Java代码

class MyOrientationListener extends WindowOrientationListener {
MyOrientationListener(Context context) {
super(context);
}
@Override
publicvoid onOrientationChanged(int rotation) {
// Send updates based on orientation value
if (true) Log.i(TAG, "onOrientationChanged, rotation changed to " +rotation);
try {
mWindowManager.setRotation(rotation, false,
mFancyRotationAnimation);
} catch (RemoteException e) {
// Ignore
}
}
}
MyOrientationListener mOrientationListener;
boolean useSensorForOrientationLp(int appOrientation) {
if (appOrientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR) {
returntrue;
}
if (mAccelerometerDefault != 0 && (
appOrientation == ActivityInfo.SCREEN_ORIENTATION_USER ||
appOrientation == ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED)) {
returntrue;
}
returnfalse;
}
/*
* We always let the sensor be switched on by default except when
* the user has explicitly disabled sensor based rotation or when the
* screen is switched off.
*/
boolean needSensorRunningLp() {
if (mCurrentAppOrientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR) {
// If the application has explicitly requested to follow the
// orientation, then we need to turn the sensor or.
returntrue;
}
if (mAccelerometerDefault == 0) {
// If the setting for using the sensor by default is enabled, then
// we will always leave it on. Note that the user could go to
// a window that forces an orientation that does not use the
// sensor and in theory we could turn it off... however, when next
// turning it on we won't have a good value for the current
// orientation for a little bit, which can cause orientation
// changes to lag, so we'd like to keep it always on. (It will
// still be turned off when the screen is off.)
returnfalse;
}
returntrue;
}

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在 WindowOrientationListener（见文件 javaframeworks/base/core/java/android/view/WindowOrientationListener.java）中会监听Sensor的值，对旋转方向进行判断，然后调用抽象方法 onOrientationChanged，因此，只要在子类 Listener中重新实现这个函数即可对四个不同方向做出响应（见上面让屏幕旋转即是一例）。

遗憾的是在 Donut和 Éclair中，对旋转方向的识别只给出了 90度旋转，在 Froyo中增加了一个 270度旋转，不支持 180度即倒立的操作。

可以在修改下面代码，判断来自于 Gsensor的值，识别出旋转方向：

public void onSensorChanged(SensorEvent event) {
float [] values = event.values;
float X = values[_DATA_X];
float Y = values[_DATA_Y];
float Z = values[_DATA_Z];
float OneEightyOverPi = 57 .29577957855f;
float gravity = ( float ) Math.sqrt(X*X+Y*Y+Z*Z);
float zyangle = ( float )Math.asin(Z/gravity)*OneEightyOverPi;
int rotation = - 1 ;
if ((zyangle <= PIVOT_UPPER) && (zyangle >= PIVOT_LOWER)) {
// Check orientation only if the phone is flat enough
// Don't trust the angle if the magnitude is small compared to the y value
float angle = ( float )Math.atan2(Y, -X) * OneEightyOverPi;
int orientation = 90 - ( int )Math.round(angle);
// normalize to 0 - 359 range
while (orientation >= 360 ) {
orientation -= 360 ;
}
while (orientation < 0 ) {
orientation += 360 ;
}
// Orientation values between LANDSCAPE_LOWER and PL_LOWER
// are considered landscape.
// Ignore orientation values between 0 and LANDSCAPE_LOWER
// For orientation values between LP_UPPER and PL_LOWER,
// the threshold gets set linearly around PIVOT.
if ((orientation >= PL_LOWER) && (orientation <= LP_UPPER)) {
float threshold;
float delta = zyangle - PIVOT;
if (mSensorRotation == Surface.ROTATION_90) {
if (delta < 0 ) {
// Delta is negative
threshold = LP_LOWER - (LP_LF_LOWER * delta);
} else {
threshold = LP_LOWER + (LP_LF_UPPER * delta);
}
rotation = (orientation >= threshold) ? Surface.ROTATION_0 : Surface.ROTATION_90;
} else {
if (delta < 0 ) {
// Delta is negative
threshold = PL_UPPER+(PL_LF_LOWER * delta);
} else {
threshold = PL_UPPER-(PL_LF_UPPER * delta);
}
rotation = (orientation <= threshold) ? Surface.ROTATION_90: Surface.ROTATION_0;
}
} else if ((orientation >= LANDSCAPE_LOWER) && (orientation < LP_LOWER)) {
rotation = Surface.ROTATION_90;
} else if ((orientation >= PL_UPPER) || (orientation <= PORTRAIT_LOWER)) {
rotation = Surface.ROTATION_0;
}
if ((rotation != - 1 ) && (rotation != mSensorRotation)) {
mSensorRotation = rotation;
onOrientationChanged(mSensorRotation);
}
}
}

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Java代码

publicvoid onSensorChanged(SensorEvent event) {
float[] values = event.values;
float X = values[_DATA_X];
float Y = values[_DATA_Y];
float Z = values[_DATA_Z];
float OneEightyOverPi = 57.29577957855f;
float gravity = (float) Math.sqrt(X*X+Y*Y+Z*Z);
float zyangle = (float)Math.asin(Z/gravity)*OneEightyOverPi;
int rotation = -1;
if ((zyangle <= PIVOT_UPPER) && (zyangle >= PIVOT_LOWER)) {
// Check orientation only if the phone is flat enough
// Don't trust the angle if the magnitude is small compared to the y value
float angle = (float)Math.atan2(Y, -X) * OneEightyOverPi;
int orientation = 90 - (int)Math.round(angle);
// normalize to 0 - 359 range
while (orientation >= 360) {
orientation -= 360;
}
while (orientation < 0) {
orientation += 360;
}
// Orientation values between LANDSCAPE_LOWER and PL_LOWER
// are considered landscape.
// Ignore orientation values between 0 and LANDSCAPE_LOWER
// For orientation values between LP_UPPER and PL_LOWER,
// the threshold gets set linearly around PIVOT.
if ((orientation >= PL_LOWER) && (orientation <= LP_UPPER)) {
float threshold;
float delta = zyangle - PIVOT;
if (mSensorRotation == Surface.ROTATION_90) {
if (delta < 0) {
// Delta is negative
threshold = LP_LOWER - (LP_LF_LOWER * delta);
} else {
threshold = LP_LOWER + (LP_LF_UPPER * delta);
}
rotation = (orientation >= threshold) ? Surface.ROTATION_0 : Surface.ROTATION_90;
} else {
if (delta < 0) {
// Delta is negative
threshold = PL_UPPER+(PL_LF_LOWER * delta);
} else {
threshold = PL_UPPER-(PL_LF_UPPER * delta);
}
rotation = (orientation <= threshold) ? Surface.ROTATION_90: Surface.ROTATION_0;
}
} elseif ((orientation >= LANDSCAPE_LOWER) && (orientation < LP_LOWER)) {
rotation = Surface.ROTATION_90;
} elseif ((orientation >= PL_UPPER) || (orientation <= PORTRAIT_LOWER)) {
rotation = Surface.ROTATION_0;
}
if ((rotation != -1) && (rotation != mSensorRotation)) {
mSensorRotation = rotation;
onOrientationChanged(mSensorRotation);
}
}
}

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在Froyo中，对上述算法进行了修改，让其报出270度的旋转方向。

Android Sensor 屏幕360度旋转实现

修改下面函数

void android.view.WindowOrientationListener SensorEventListenerImp.onSensorChanged(android.hardware.SensorEvent event)
float[] values = event.values;
float X = values[_DATA_X];
float Y = values[_DATA_Y];
float Z = values[_DATA_Z];
//For fixing the problem of Sensor change the window orientation error but the sensor game is no problem.
float OneEightyOverPi = 57.29577957855f;
float gravity = (float) Math.sqrt(X*X+Y*Y+Z*Z);
float zyangle = (float)Math.asin(Z/gravity)*OneEightyOverPi;
int rotation = -1;
if ((zyangle <= PIVOT_UPPER) && (zyangle >= PIVOT_LOWER)) {
// Check orientation only if the phone is flat enough
// Don't trust the angle if the magnitude is small compared to the y value
float angle = (float)Math.atan2(Y, -X) * OneEightyOverPi;
int orientation = 90 - (int)Math.round(angle);
// normalize to 0 - 359 range
while (orientation >= 360) {
orientation -= 360;
}
while (orientation < 0) {
orientation += 360;
}
Log.i("Tiger","orientation="+orientation);
//确定由角度与屏幕方向的对应范围
if(orientation > 325 || orientation <= 45){
rotation = Surface.ROTATION_0;
}else if(orientation > 45 && orientation <= 135){
rotation = Surface.ROTATION_270;
}else if(orientation > 135 && orientation < 225){
rotation = Surface.ROTATION_180;
}else {
rotation = Surface.ROTATION_90;
}
Log.i("Tiger","mSensorRotation="+mSensorRotation+" , rotation="+rotation);
if ((rotation != -1) && (rotation != mSensorRotation)) {
mSensorRotation = rotation;
onOrientationChanged(mSensorRotation);
}
}