Android修改横屏的默认角度为顺时针270度

默认的横屏角度是顺时针90度，修改为顺时针270度，即是逆时针90度。

1.查看相关逻辑，可以看到有个布尔值com.android.internal.R.bool.config_reverseDefaultRotation控制翻转：

frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

  @Override
    public void setInitialDisplaySize(Display display, int width, int height, int density) {
        // This method might be called before the policy has been fully initialized
        // or for other displays we don't care about.
        if (mContext == null || display.getDisplayId() != Display.DEFAULT_DISPLAY) {
            return;
        }
        mDisplay = display;

        final Resources res = mContext.getResources();
        int shortSize, longSize;
        if (width > height) {
            shortSize = height;
            longSize = width;
            mLandscapeRotation = Surface.ROTATION_0;
            mSeascapeRotation = Surface.ROTATION_180;
            if (res.getBoolean(com.android.internal.R.bool.config_reverseDefaultRotation)) {
                mPortraitRotation = Surface.ROTATION_90;
                mUpsideDownRotation = Surface.ROTATION_270;
            } else {
                mPortraitRotation = Surface.ROTATION_270;
                mUpsideDownRotation = Surface.ROTATION_90;
            }
        } else {
            shortSize = width;
            longSize = height;
            mPortraitRotation = Surface.ROTATION_0;
            mUpsideDownRotation = Surface.ROTATION_180;
            if (res.getBoolean(com.android.internal.R.bool.config_reverseDefaultRotation)) {
                mLandscapeRotation = Surface.ROTATION_270;
                mSeascapeRotation = Surface.ROTATION_90;
            } else {
                mLandscapeRotation = Surface.ROTATION_90;
                mSeascapeRotation = Surface.ROTATION_270;
            }
        }

        mStatusBarHeight =
                res.getDimensionPixelSize(com.android.internal.R.dimen.status_bar_height);

        // Height of the navigation bar when presented horizontally at bottom
        mNavigationBarHeightForRotation[mPortraitRotation] =
        mNavigationBarHeightForRotation[mUpsideDownRotation] =
                res.getDimensionPixelSize(com.android.internal.R.dimen.navigation_bar_height);
        mNavigationBarHeightForRotation[mLandscapeRotation] =
        mNavigationBarHeightForRotation[mSeascapeRotation] = res.getDimensionPixelSize(
                com.android.internal.R.dimen.navigation_bar_height_landscape);

        // Width of the navigation bar when presented vertically along one side
        mNavigationBarWidthForRotation[mPortraitRotation] =
        mNavigationBarWidthForRotation[mUpsideDownRotation] =
        mNavigationBarWidthForRotation[mLandscapeRotation] =
        mNavigationBarWidthForRotation[mSeascapeRotation] =
                res.getDimensionPixelSize(com.android.internal.R.dimen.navigation_bar_width);

        // SystemUI (status bar) layout policy
        int shortSizeDp = shortSize * DisplayMetrics.DENSITY_DEFAULT / density;
        int longSizeDp = longSize * DisplayMetrics.DENSITY_DEFAULT / density;

        // Allow the navigation bar to move on small devices (phones).
        
        /// M: read the critical dp from mtk resource @{
        //mNavigationBarCanMove = shortSizeDp < 600;
        mNavigationBarCanMove = shortSizeDp < mContext.getResources().getInteger(
            com.mediatek.internal.R.integer.config_dp_for_rotation);
        /// @}
        mHasNavigationBar = res.getBoolean(com.android.internal.R.bool.config_showNavigationBar);

        /// M:[SmartBook]Don't show navigation bar if SmartBook plugged in @{
        if (FeatureOption.MTK_SMARTBOOK_SUPPORT) {
            mNavigationBarCanMove = false;
            mHasNavigationBar = mSmartBookPlugIn ? false : mContext.getResources().getBoolean(
                com.android.internal.R.bool.config_showNavigationBar);
            Slog.d(TAG, "mSmartBookPlugIn:" + mSmartBookPlugIn + ", mHasNavigationBar:" + mHasNavigationBar);
        }
        /// @}

        // Allow a system property to override this. Used by the emulator.
        // See also hasNavigationBar().
        String navBarOverride = SystemProperties.get("qemu.hw.mainkeys");
        if ("1".equals(navBarOverride)) {
            mHasNavigationBar = false;
        } else if ("0".equals(navBarOverride)) {
            mHasNavigationBar = true;
        }

        // For demo purposes, allow the rotation of the HDMI display to be controlled.
        // By default, HDMI locks rotation to landscape.
        if ("portrait".equals(SystemProperties.get("persist.demo.hdmirotation"))) {
            mDemoHdmiRotation = mPortraitRotation;
        } else {
            mDemoHdmiRotation = mLandscapeRotation;
        }
        mDemoHdmiRotationLock = SystemProperties.getBoolean("persist.demo.hdmirotationlock", false);

        // Only force the default orientation if the screen is xlarge, at least 960dp x 720dp, per
        // http://developer.android.com/guide/practices/screens_support.html#range
        mForceDefaultOrientation = longSizeDp >= 960 && shortSizeDp >= 720 &&
                res.getBoolean(com.android.internal.R.bool.config_forceDefaultOrientation) &&
                // For debug purposes the next line turns this feature off with:
                // $ adb shell setprop config.override_forced_orient true
                // $ adb shell wm size reset
                !"true".equals(SystemProperties.get("config.override_forced_orient"));
    }

<!-- If true, the direction rotation is applied to get to an application's requested
         orientation is reversed.  Normally, the model is that landscape is
         clockwise from portrait; thus on a portrait device an app requesting
         landscape will cause a clockwise rotation, and on a landscape device an
         app requesting portrait will cause a counter-clockwise rotation.  Setting
         true here reverses that logic. -->
    <bool name="config_reverseDefaultRotation">true</bool>