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     }      @Override     public void fillInLogContainerData(View v, ItemInfo info, Target target, Target targetParent) {         target.gridX = info.cellX;         target.gridY = info.cellY;         targetParent.containerType = LauncherLogProto.ContainerType.HOTSEAT;     }      @Override     public 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);     }      @Override     public boolean onTouchEvent(MotionEvent event) {         // Don't let if follow through to workspace         return true;     }      @Override     public 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                                      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