Android Launhcer 左屏实现以及左屏作为默认显示屏幕实现方法

在Launcher.java

protected boolean hasCustomContentToLeft() {
        //return false;
    return true;//负一屏开关打开  wanchengguo 20180424

    }

    /**
     * To be overridden by subclasses to populate the custom content container and call
     * {@link #addToCustomContentPage}. This will only be invoked if
     * {@link #hasCustomContentToLeft()} is {@code true}.
     */


    protected void populateCustomContentContainer() {
    /*wanchengguo 负一屏加载布局 20180424 begin*/


    View negativeviews = getLayoutInflater().inflate(R.layout.my_negative_layout, null);//加载的布局
    initData();//数据、view初始化


    addToCustomContentPage(negativeviews, mWorkspace.getCustomContentCallbacks(), "custom view");  
    /*wanchengguo 负一屏加载布局 20180424 end*/

    }

默认显示左屏：

默认显示哪一屏设置方法： launcher:defaultScreen

res/layout/launcher.xml//  Launcher.java 加载的布局

.....

 <com.android.launcher3.Workspace
            android:id="@+id/workspace"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_gravity="center"

            launcher:defaultScreen="@integer/config_workspaceDefaultScreen" />

.......

Workspace.java

 public void createCustomContentContainer() {
        CellLayout customScreen = (CellLayout)
                mLauncher.getLayoutInflater().inflate(R.layout.workspace_screen, null);
        customScreen.disableBackground();
        customScreen.disableDragTarget();


        mWorkspaceScreens.put(CUSTOM_CONTENT_SCREEN_ID, customScreen);
        mScreenOrder.add(0, CUSTOM_CONTENT_SCREEN_ID);


        // We want no padding on the custom content
        customScreen.setPadding(0, 0, 0, 0);


        addFullScreenPage(customScreen);


        // Ensure that the current page and default page are maintained.
        mDefaultPage = mOriginalDefaultPage /*+ 1*/;//添加左屏时 默认显示页数不加1，目的是让左屏是默认显示页 当设置默认显示屏为0时 wanchengguo 20180428


        // Update the custom content hint
        if (mRestorePage != INVALID_RESTORE_PAGE) {
            mRestorePage = mRestorePage + 1;
        } else {
            setCurrentPage(getCurrentPage() + 1);
        }
    }