探秘 widget 之 launcher 添加 widget 的流程分析

最近打算研究下android的widget相关问题，并把一些心得在此稍作记录，哈哈，等研究完成了，如果有必要的话，也会把改动的源码贴出来，以飨读者。今天先来看看launcher2中添加widget的流程。

添加widget首先需要在laucher的空白处长按，所以首先定位在laucher的 public boolean onLongClick(View v) 中，看到：

01if (mWorkspace.allowLongPress()) {  

02    if (cellInfo.cell == null) {  

03        if (cellInfo.valid) {  

04            // User long pressed on empty space  

05            mWorkspace.setAllowLongPress(false);  

06            mWorkspace.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,  

07                    HapticFeedbackConstants.FLAG_IGNORE_VIEW_SETTING);  

08            showAddDialog(cellInfo);  

09        }  

10    } else {  

11        if (!(cellInfo.cell instanceof Folder)) {  

12            // User long pressed on an item  

13            mWorkspace.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,  

14                    HapticFeedbackConstants.FLAG_IGNORE_VIEW_SETTING);  

15            mWorkspace.startDrag(cellInfo);  

16        }  

17    }  

18}

可以看到跳转到了showAddDialog(cellInfo)，寻找到：

1private void showAddDialog(CellLayout.CellInfo cellInfo) {  

2    mAddItemCellInfo = cellInfo;  

3    mWaitingForResult = true;  

4    showDialog(DIALOG_CREATE_SHORTCUT);  

5}

可以看到他携带着DIALOG_CREATE_SHORTCUT参数创建了一个Dialog，携带参数跳入Launcher.java的父类Activity.java的showDialog()方法,最终到达Launcher.java的onCreateDialog(int id)方法,代码如下:

01@Override 

02protected Dialog onCreateDialog(int id) {  

03    switch (id) {  

04        case DIALOG_CREATE_SHORTCUT:  

05            return new CreateShortcut().createDialog();  

06        case DIALOG_RENAME_FOLDER:  

07            return new RenameFolder().createDialog();  

08    }  

09   

10    return super.onCreateDialog(id);  

11}

跳转到了CreateShortcut()的createDialog()方法：

01Dialog createDialog() {  

02    mWaitingForResult = true;   

03    mAdapter = new AddAdapter(Launcher.this);   

04    final AlertDialog.Builder builder = newAlertDialog.Builder(Launcher.this);      

05    builder.setTitle(getString(R.string.menu_item_add_item));  

06    builder.setAdapter(mAdapter, this);    

07    builder.setInverseBackgroundForced(true);   

08    AlertDialog dialog = builder.create();  

09    dialog.setOnCancelListener(this);  

10    dialog.setOnDismissListener(this);  

11    dialog.setOnShowListener(this);  

12   

13    return dialog;  

14}

这里可以看到一个 AddAdapter类，跳转去看看，这个就是定义长按后出现的对话框的内容：

1public static final int ITEM_SHORTCUT = 0;

2public static final int ITEM_APPWIDGET = 1;

3public static final int ITEM_LIVE_FOLDER = 2;

4public static final int ITEM_WALLPAPER = 3;

如果我们需要在原来的对话框中添加新的内容，那么首先需要修改的就是这里，我们回到之前的地方接着往下走，dialog响应的点击事件，public void onClick(DialogInterface dialog, int which) ：

01case AddAdapter.ITEM_APPWIDGET: {

02    int appWidgetId = Launcher.this.mAppWidgetHost.allocateAppWidgetId();

03    //这里生成了一个appWidgetId，供后面绑定AppWidgetProvider使用

04    Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK);

05    //新建一个intent，该intent是打开一个现实Widgets列表的activity,该activity对应类AppWidgetPickActivity  

06    pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);

07    // start the pick activity

08    //设置EXTRA_APPWIDGET_ID            

09    startActivityForResult(pickIntent, REQUEST_PICK_APPWIDGET);

10    break;

11}

这里看到点击widget条目之后，跳转打开一个新的pickIntent，其实际运行的为packages/apps/Settings/src/com/android/settings/AppWidgetPickActivity.java：

先在onCreate方法中创建了一个InstalledAppWidgets列表，该列表就是我们在界面上能见到的所有widgets。

在点击一个widgets,进入AppWidgetPickActivity.onClick事件监听，注意阅读该方法代码，它会进入else：

1if (intent.getExtras() != null) {

2    // If there are any extras, it's because this entry is custom.

3    // Don't try to bind it, just pass it back to the app.

4    setResultData(RESULT_OK, intent);

5} else {

6    try {

7        mAppWidgetManager.bindAppWidgetId(mAppWidgetId, intent.getComponent());

8        //绑定选中的桌面组件与mAppWidgetId

9        result = RESULT_OK;//设置返回结果为ok

activity执行结束后面都会进入launcher.onActivityResult,查看该函数方法有两个关键的case:

1case REQUEST_PICK_APPWIDGET:

2     addAppWidget(data);

3       break;

4case REQUEST_CREATE_APPWIDGET:

5     completeAddAppWidget(data, mAddItemCellInfo);

接着跳转到launcher的addAppWidget(Intent data)里data为传递来的appWidgetId：

01void addAppWidget(Intent data) {

02        // TODO: catch bad widget exception when sent

03        int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);

04        AppWidgetProviderInfo appWidget = mAppWidgetManager.getAppWidgetInfo(appWidgetId);

05 //先判断是否有配置页

06        if (appWidget.configure != null) {

07            // Launch over to configure widget, if needed

08            Intent intent = newIntent(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE);

09            intent.setComponent(appWidget.configure);

10            intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);

11            startActivityForResultSafely(intent, REQUEST_CREATE_APPWIDGET);

12        } else {

13            // Otherwise just add it

14            onActivityResult(REQUEST_CREATE_APPWIDGET, Activity.RESULT_OK, data);

15        }

16    }

通过onActivityResult(REQUEST_CREATE_APPWIDGET, Activity.RESULT_OK, data);跳转回launcher.onActivityResult的

case REQUEST_CREATE_APPWIDGET:

completeAddAppWidget(data, mAddItemCellInfo);

1@param data The intent describing the appWidgetId.

2     * @param cellInfo The position on screen where to create the widget.

3     */

4    private void completeAddAppWidget(Intent data, CellLayout.CellInfo cellInfo)

在 completeAddAppWidget(data, mAddItemCellInfo)中完成widget的添加。

01private void completeAddAppWidget(Intent data, CellLayout.CellInfo cellInfo) {

02        Bundle extras = data.getExtras();

03        int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);

04        if (LOGD) Log.d(TAG, "dumping extras content=" + extras.toString());

05 //由appWidgetId获取widget的信息，例如大小等

06        AppWidgetProviderInfo appWidgetInfo = mAppWidgetManager.getAppWidgetInfo(appWidgetId);

07        // Calculate the grid spans needed to fit this widget

08        CellLayout layout = (CellLayout) mWorkspace.getChildAt(cellInfo.screen);

09        int[] spans = layout.rectToCell(appWidgetInfo.minWidth, appWidgetInfo.minHeight);

10        // Try finding open space on Launcher screen

11        final int[] xy = mCellCoordinates;

12        if (!findSlot(cellInfo, xy, spans[0], spans[1])) {

13            if (appWidgetId != -1) mAppWidgetHost.deleteAppWidgetId(appWidgetId);

14            return;

15        }

16        // Build Launcher-specific widget info and save to database

17        LauncherAppWidgetInfo launcherInfo = newLauncherAppWidgetInfo(appWidgetId);

18        launcherInfo.spanX = spans[0];

19        launcherInfo.spanY = spans[1];

20        LauncherModel.addItemToDatabase(this, launcherInfo,

21                LauncherSettings.Favorites.CONTAINER_DESKTOP,

22                mWorkspace.getCurrentScreen(), xy[0], xy[1], false);

23        if (!mRestoring) {

24            mDesktopItems.add(launcherInfo);

25            // Perform actual inflation because we're live

26            launcherInfo.hostView = mAppWidgetHost.createView(this, appWidgetId, appWidgetInfo);

27            launcherInfo.hostView.setAppWidget(appWidgetId, appWidgetInfo);

28            launcherInfo.hostView.setTag(launcherInfo);

29            mWorkspace.addInCurrentScreen(launcherInfo.hostView, xy[0], xy[1],

30                    launcherInfo.spanX, launcherInfo.spanY, isWorkspaceLocked());

31        }