探秘widget之launcher添加widget的流程分析

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：
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if (mWorkspace.allowLongPress()) {    
    if (cellInfo.cell == null) {    
        if (cellInfo.valid) {    
            // User long pressed on empty space    
            mWorkspace.setAllowLongPress(false);    
            mWorkspace.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,    
                    HapticFeedbackConstants.FLAG_IGNORE_VIEW_SETTING);    
            showAddDialog(cellInfo);    
        }    
    } else {    
        if (!(cellInfo.cell instanceof Folder)) {    
            // User long pressed on an item    
            mWorkspace.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,    
                    HapticFeedbackConstants.FLAG_IGNORE_VIEW_SETTING);    
            mWorkspace.startDrag(cellInfo);    
        }    
    }    
}   

可以看到跳转到了showAddDialog(cellInfo)，寻找到：
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private void showAddDialog(CellLayout.CellInfo cellInfo) {    
    mAddItemCellInfo = cellInfo;    
    mWaitingForResult = true;    
    showDialog(DIALOG_CREATE_SHORTCUT);    
}   

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:
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@Override   
protected Dialog onCreateDialog(int id) {    
    switch (id) {    
        case DIALOG_CREATE_SHORTCUT:    
            return new CreateShortcut().createDialog();    
        case DIALOG_RENAME_FOLDER:    
            return new RenameFolder().createDialog();    
    }    
   
    return super.onCreateDialog(id);    
}   

跳转到了CreateShortcut()的createDialog()方法：
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Dialog createDialog() {    
    mWaitingForResult = true;     
    mAdapter = new AddAdapter(Launcher.this);     
    final AlertDialog.Builder builder = new AlertDialog.Builder(Launcher.this);       builder.setTitle(getString(R.string.menu_item_add_item));    
    builder.setAdapter(mAdapter, this);      
    builder.setInverseBackgroundForced(true);     
    AlertDialog dialog = builder.create();    
    dialog.setOnCancelListener(this);    
    dialog.setOnDismissListener(this);    
    dialog.setOnShowListener(this);    
   
    return dialog;    
}   

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：
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public static final int ITEM_SHORTCUT = 0; 
    public static final int ITEM_APPWIDGET = 1; 
    public static final int ITEM_LIVE_FOLDER = 2; 
    public 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) ：
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case AddAdapter.ITEM_APPWIDGET: { 
                    int appWidgetId = Launcher.this.mAppWidgetHost.allocateAppWidgetId(); 
//这里生成了一个appWidgetId，供后面绑定AppWidgetProvider使用 
                    Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK); 
//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    
                pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId); 
                    // start the pick activity 
       //设置EXTRA_APPWIDGET_ID             startActivityForResult(pickIntent, REQUEST_PICK_APPWIDGET); 
                    break; 
                } 


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：
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if (intent.getExtras() != null) { 
            // If there are any extras, it's because this entry is custom. 
            // Don't try to bind it, just pass it back to the app. 
            setResultData(RESULT_OK, intent); 
        } else { 
            try { 
                mAppWidgetManager.bindAppWidgetId(mAppWidgetId, intent.getComponent()); 
//绑定选中的桌面组件与mAppWidgetId 
        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:
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case REQUEST_PICK_APPWIDGET: 
     addAppWidget(data); 
       break; 
case REQUEST_CREATE_APPWIDGET: 
     completeAddAppWidget(data, mAddItemCellInfo); 


接着跳转到launcher的addAppWidget(Intent data)里data为传递来的appWidgetId：
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void addAppWidget(Intent data) { 
        // TODO: catch bad widget exception when sent 
        int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, -1); 
        AppWidgetProviderInfo appWidget = mAppWidgetManager.getAppWidgetInfo(appWidgetId); 
//先判断是否有配置页 
        if (appWidget.configure != null) { 
            // Launch over to configure widget, if needed 
            Intent intent = new Intent(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE); 
            intent.setComponent(appWidget.configure); 
            intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId); 
            startActivityForResultSafely(intent, REQUEST_CREATE_APPWIDGET); 
        } else { 
            // Otherwise just add it 
            onActivityResult(REQUEST_CREATE_APPWIDGET, Activity.RESULT_OK, data); 
        } 
    } 


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

case REQUEST_CREATE_APPWIDGET:
          completeAddAppWidget(data, mAddItemCellInfo);


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@param data The intent describing the appWidgetId. 
     * @param cellInfo The position on screen where to create the widget. 
     */ 
    private void completeAddAppWidget(Intent data, CellLayout.CellInfo cellInfo) 

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

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private void completeAddAppWidget(Intent data, CellLayout.CellInfo cellInfo) { 
        Bundle extras = data.getExtras(); 
        int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1); 
        if (LOGD) Log.d(TAG, "dumping extras content=" + extras.toString()); 
//由appWidgetId获取widget的信息，例如大小等 
        AppWidgetProviderInfo appWidgetInfo = mAppWidgetManager.getAppWidgetInfo(appWidgetId); 
        // Calculate the grid spans needed to fit this widget 
        CellLayout layout = (CellLayout) mWorkspace.getChildAt(cellInfo.screen); 
        int[] spans = layout.rectToCell(appWidgetInfo.minWidth, appWidgetInfo.minHeight); 
        // Try finding open space on Launcher screen 
        final int[] xy = mCellCoordinates; 
        if (!findSlot(cellInfo, xy, spans[0], spans[1])) { 
            if (appWidgetId != -1) mAppWidgetHost.deleteAppWidgetId(appWidgetId); 
            return; 
        } 
        // Build Launcher-specific widget info and save to database 
        LauncherAppWidgetInfo launcherInfo = new LauncherAppWidgetInfo(appWidgetId); 
        launcherInfo.spanX = spans[0]; 
        launcherInfo.spanY = spans[1]; 
        LauncherModel.addItemToDatabase(this, launcherInfo, 
                LauncherSettings.Favorites.CONTAINER_DESKTOP, 
                mWorkspace.getCurrentScreen(), xy[0], xy[1], false); 
        if (!mRestoring) { 
            mDesktopItems.add(launcherInfo); 
            // Perform actual inflation because we're live 
            launcherInfo.hostView = mAppWidgetHost.createView(this, appWidgetId, appWidgetInfo); 
            launcherInfo.hostView.setAppWidget(appWidgetId, appWidgetInfo); 
            launcherInfo.hostView.setTag(launcherInfo); 
            mWorkspace.addInCurrentScreen(launcherInfo.hostView, xy[0], xy[1], 
                    launcherInfo.spanX, launcherInfo.spanY, isWorkspaceLocked()); 
        }