1.前言

在10.0的系统rom定制化开发中，在对于launcher3的一些开发定制中，在对hotseat的一些开发中，需要实现动态hotseat居中
的功能，就是在拖拽图标进入和拖出hotseat，都可以保持hotseat居中的功能，接下来分析下相关功能实现
具体如图:

2.Launcher3拖拽图标进入hotseat自适应布局功能实现一的核心类

packages\apps\Launcher3\src\com\android\launcher3\Hotseat.java

3.Launcher3拖拽图标进入hotseat自适应布局功能实现一的核心功能分析和实现

Launcher顾名思义,就是桌面的意思,也是android系统启动后第一个启动的应用程序,
:Launcher3负责管理和展示用户手机桌面上的各个应用程序图标。它通过GridView或者LinearLayout等布局管理器将
图标进行排列,并支持滑动、放大缩小等手势操作
Hotseat也是属于在导航栏底部的BubbleTextView的布局，只是不显示app图标

3.1 Hotseat.java相关添加背景功能分析

在实现Launcher3拖拽图标进入hotseat自适应布局功能实现一的核心功能中，通过上述的分析得知，
首选需要给Hotseat添加背景功能，然后需要根据hotseat的数量多少来设置hotseat的宽度高度等
相关参数，这样就实现了第一步的hotseat的居中显示功能，

public class Hotseat extends CellLayout implements LogContainerProvider, Insettable, Transposable {@ViewDebug.ExportedProperty(category = "launcher")public boolean mHasVerticalHotseat;private final HotseatController mController;public Hotseat(Context context) {this(context, null);}public Hotseat(Context context, AttributeSet attrs) {this(context, attrs, 0);}public Hotseat(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);mController = LauncherAppMonitor.getInstance(context).getHotseatController();}public HotseatController getController() {return mController;}/* Get the orientation specific coordinates given an invariant order in the hotseat. */public int getCellXFromOrder(int rank) {return mHasVerticalHotseat ? 0 : rank;}public int getCellYFromOrder(int rank) {return mHasVerticalHotseat ? (getCountY() - (rank + 1)) : 0;}public void resetLayout(boolean hasVerticalHotseat) {removeAllViewsInLayout();mHasVerticalHotseat = hasVerticalHotseat;InvariantDeviceProfile idp = mActivity.getDeviceProfile().inv;if (hasVerticalHotseat) {setGridSize(1, idp.numHotseatIcons);} else {setGridSize(idp.numHotseatIcons, 1);}//add core start// 添加背景if(idp.numHotseatIcons>0){setBackgroundResource(R.drawable.shape_corner);}//add core end}@Overridepublic void fillInLogContainerData(View v, ItemInfo info, Target target, Target targetParent) {target.gridX = info.cellX;target.gridY = info.cellY;targetParent.containerType = LauncherLogProto.ContainerType.HOTSEAT;}@Overridepublic void setInsets(Rect insets) {FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) getLayoutParams();DeviceProfile grid = mActivity.getWallpaperDeviceProfile();insets = grid.getInsets();if (grid.isVerticalBarLayout()) {lp.height = ViewGroup.LayoutParams.WRAP_CONTENT;if (grid.isSeascape()) {lp.gravity = Gravity.LEFT;lp.width = grid.hotseatBarSizePx + insets.left;} else {lp.gravity = Gravity.RIGHT;lp.width = grid.hotseatBarSizePx + insets.right;}} else {lp.gravity = Gravity.BOTTOM;lp.width = ViewGroup.LayoutParams.MATCH_PARENT;lp.height = grid.hotseatBarSizePx + insets.bottom;}Rect padding = grid.getHotseatLayoutPadding();setPadding(padding.left, padding.top, padding.right, padding.bottom);setLayoutParams(lp);InsettableFrameLayout.dispatchInsets(this, insets);}@Overridepublic boolean onTouchEvent(MotionEvent event) {// Don't let if follow through to workspacereturn true;}@Overridepublic RotationMode getRotationMode() {return Launcher.getLauncher(getContext()).getRotationMode();}
}

在实现Launcher3拖拽图标进入hotseat自适应布局功能实现一的核心功能中，通过上述的分析得知，
在Hotseat中相关源码分析，可以发现由
resetLayout 就是负责布局的 当hotseat 增加减少时都会重新布局
所以在setBackgroundResource(R.drawable.shape_corner);添加背景就可以了

  public void resetLayout(boolean hasVerticalHotseat) {removeAllViewsInLayout();mHasVerticalHotseat = hasVerticalHotseat;InvariantDeviceProfile idp = mActivity.getDeviceProfile().inv;if (hasVerticalHotseat) {setGridSize(1, idp.numHotseatIcons);} else {setGridSize(idp.numHotseatIcons, 1);}// 添加背景if(idp.numHotseatIcons>0){setBackgroundResource(R.drawable.shape_corner);}}shape_corner.xml<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"><!--背景颜色--><solid android:color="#FFFAFA" /><!--角的半径--><corners android:radius="10dp"/><!--边框颜色--><stroke android:width="1dp" android:color="#00000000" />
</shape>public void setInsets(Rect insets) {FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) getLayoutParams();DeviceProfile grid = mActivity.getWallpaperDeviceProfile();insets = grid.getInsets();//竖屏布局if (grid.isVerticalBarLayout()) {lp.height = ViewGroup.LayoutParams.WRAP_CONTENT;if (grid.isSeascape()) {lp.gravity = Gravity.LEFT;lp.width = grid.hotseatBarSizePx + insets.left;} else {lp.gravity = Gravity.RIGHT;lp.width = grid.hotseatBarSizePx + insets.right;}} else {//modify core start// 横屏布局// 平板开发项目 固定横屏，所以要在这里设置参数// 设置宽高  左边底部的间距InvariantDeviceProfile idp = mActivity.getDeviceProfile().inv;int hotseatNums = idp.numHotseatIcons;lp.width = hotseatNums*grid.hotseatBarSizePx+(hotseatNums+1)*dip2px(15.0f);lp.height = grid.hotseatBarSizePx + insets.bottom;if(getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT){lp.leftMargin = (int)((1080-lp.width)/2);}else{lp.leftMargin = (int)((1920-lp.width)/2);}lp.gravity = Gravity.BOTTOM;//modify core end}Rect padding = grid.getHotseatLayoutPadding();// 设置padding 布局setPadding(0, padding.top, 0,0);setLayoutParams(lp);InsettableFrameLayout.dispatchInsets(this, insets);}

在实现Launcher3拖拽图标进入hotseat自适应布局功能实现一的核心功能中，通过上述的分析得知，
在Hotseat中相关源码分析，
而setInset() 负责设置绘制布局 的参数 这里设置hotseat的宽高等参数布局
其实只需要修改lp的参数就行了 然后hotseat 会根据长宽等参数 来具体布局每一个hotseat的具体坐标
根据横竖屏来确定lp.leftMargin的值，就可以保证居中显示