Android 2.1实现屏幕不同方向旋转

最近调g-sensor的过程中发现Android2.1在设置界面横竖屏幕旋转时只有两个方向，而且板子横着时显示竖屏，竖着时显示横屏（前一版硬件可没这个问题，看来是硬件工程师将g-sensor模块贴片方向改变）。

为了解决横竖颠倒的问题，干脆用最简单的方法：在g-sensor驱动中在input_report_abs()函数上报前将x、y轴交换，z轴不变。

short temp;
temp = x;
x = y;
y = temp;
input_report_abs(mma_abs_dev, ABS_X, x);    
input_report_abs(mma_abs_dev, ABS_Y, y);    
input_report_abs(mma_abs_dev, ABS_Z, z);
input_report_abs(mma_abs_dev, ABS_RX, tilt);
input_sync(mma_abs_dev);

横竖颠倒解决了，但只有两个方向旋转（0度、90度），我可是需要四个方向啊，研究了下framework代码，发现Android是支持四个方向的，分别是：ROTATION_0、ROTATION_90、ROTATION_180、ROTATION_270，在板子上试了下Android2.2发现有3个方向，而Android2.1只有2个，既然是版本的问题，那就直接修改框架层代码，找了半天终于发现只要修改文件frameworks/base/core/java/android/view/WindowOrientationListener.java

修改代码：

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(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;
                }        
                if ((rotation != -1) && (rotation != mSensorRotation)) {
                    mSensorRotation = rotation;
                    onOrientationChanged(mSensorRotation);
                }
            }
        }

哈哈，四个方向旋转都可以了！