公司想做一个半屏功能，就是下拉屏幕显示一半；刚开始在网上找了很久，都没有相关的经验可以借鉴；最后只能靠自己去源码里面寻找方法了；
不多说，直接上代码：
1）先上触发调用的方法
try {
SystemProperties.set(“com.bsd.zoom.mode”,“1”);
DisplayManager dm = (DisplayManager) mContext.getSystemService(Context.DISPLAY_SERVICE);
Class<?> cDisplay = Class.forName(“android.hardware.display.DisplayManager”);
Method singleHandMet = cDisplay.getMethod(“singleHandModeChange”, boolean.class, boolean.class);
singleHandMet.invoke(dm, true,true);
}catch (Exception e){
e.printStackTrace();
}
（注：SystemProperties.set(“com.bsd.zoom.mode”,“1”);是判断半屏还是全屏，下面的放射方法是调用frameworks刷新界面）

2）frameworks\base\core\java\android\hardware\display\DisplayManager.java；
添加以下方法
public void singleHandModeChange(boolean change, boolean left){
mGlobal.singleHandModeChange(change,left);
}
3）frameworks\base\core\java\android\hardware\display\DisplayManagerGlobal.java；
添加以下方法
public void singleHandModeChange(boolean change,boolean left){
try{
mDm.singleHandModeChange(change,left);
}catch(RemoteException ex){
Log.w(“SingleHandMode”,“SingleHandMode Failed to singleHandChange error:”+ex.toString());
}
}
4）frameworks\base\core\java\android\hardware\display\IDisplayManager.aidl；
添加以下方法：
void singleHandModeChange(boolean change,boolean left);
5）frameworks\base\services\core\java\com\android\server\display\DisplayManagerService.java；
在BinderService内部类下添加：
private final SurfaceControl.Transaction mDisplayTransaction = new SurfaceControl.Transaction();
@Override // Binder call
public void singleHandModeChange(boolean change, boolean left) {
// mSingleHandModeState = change;
//mSingleHandModeLeft = left;
scheduleTraversalLocked(false);
performTraversalInternal(mDisplayTransaction);
}
6)frameworks\base\services\core\java\com\android\server\wm\WindowStateAnimator.java;
import android.os.SystemProperties;
在void setSurfaceBoundariesLocked(final boolean recoveringMemory)方法下
if (!w.mSeamlesslyRotated)判断语句内添加
if(SystemProperties.get(“com.bsd.zoom.mode”).equals(“1”)){
mTmpSize.top = 540;
}
//mSurfaceController.setPositionInTransaction(xOffset, yOffset, recoveringMemory);
mSurfaceController.setPositionInTransaction(mTmpSize.left, mTmpSize.top, recoveringMemory);
7）frameworks\base\services\core\java\com\android\server\display\LogicalDisplay.java；
在configureDisplayLocked方法里添加
String zoomState = SystemProperties.get(“com.bsd.zoom.mode”);
if(!zoomState.equals("") && zoomState != null){
if(zoomState.equals(“1”)){//降一半
mTempLayerStackRect.set(0, -displayInfo.logicalHeight/2, displayInfo.logicalWidth, displayInfo.logicalHeight/2);
}else{//复原
mTempLayerStackRect.set(0, 0, displayInfo.logicalWidth, displayInfo.logicalHeight);
}
}else{
mTempLayerStackRect.set(0, 0, displayInfo.logicalWidth, displayInfo.logicalHeight);
}
还有
int displayRectTop = (physHeight - displayRectHeight) / 2;
int displayRectLeft = (physWidth - displayRectWidth) / 2;

	if(!zoomState.equals("") && zoomState != null){
		if(zoomState.equals("1")){//降一半-触摸
			displayRectTop = displayRectHeight/2;
			displayRectLeft = 0;
		}
	}