前言

Launcher在Android的AppWidget整個(gè)體系中扮演AppWidgetHost的角色，本文分析Launcher對(duì)于AppWidget的處理 部分源碼分析。

一、AppWidget加載流程

1. Android系統(tǒng)啟動(dòng)，SystemServer創(chuàng)建AppWidgetService，并調(diào)用systemReady()方法，在systemReady()方法中做以下三項(xiàng)準(zhǔn)備工作：

1. 通過PackageManager從Android系統(tǒng)中查找所有已經(jīng)被安裝的AppWidget（包含"android.appwidget.action.APPWIDGET_UPDATE“ 的Action和meta-data標(biāo)簽），解析AppWidget的配置信息，封閉成對(duì)象，保存到List集合。
2. 從/data/system/users/0/appwidgets.xml文件讀取已經(jīng)被添加到Launcher的AppWidget信息，封閉成對(duì)象，保存到List集合中。
3. 注冊(cè)四個(gè)廣播接收器：第一. Android系統(tǒng)啟動(dòng)完成，第二. Android配置信息改變，第三. 添加刪除應(yīng)用，第四. sdcard的安裝與缷載。

2. Android系統(tǒng)啟動(dòng)Launcher應(yīng)用程序,會(huì)做以下準(zhǔn)備工作：

1. 從Launcher應(yīng)用的數(shù)據(jù)庫查找已經(jīng)被添加到Launcher的AppWidget信息。
2. 根據(jù)查找到的appWidgetId值（整型值）創(chuàng)建LauncherAppWidgetHostView布局對(duì)象。
3. 根據(jù)查找到的appWidgetId值（整型值）從AppWidgetService中獲取RemoteViews對(duì)象（因?yàn)槭堑谝淮螁?dòng)所以RemoteViews對(duì)象為空）。
4. 將獲取到的RemoteViews對(duì)象的布局解析并設(shè)置到第（2）步中創(chuàng)建的LauncherAppWidgetHostView布局對(duì)象中。
5. 將LauncherAppWidgetHostView布局對(duì)象添加到Launcher的WorkSpace中（因?yàn)镽emoteViews對(duì)象為空，所以只在Launcher的 WorkSpace中占了一個(gè)位置）。

3. Android系統(tǒng)啟動(dòng)完成，發(fā)出BOOT_COMPLETED廣播，AppWidgetService接收到廣播后，會(huì)做以下事情：

1. 獲取已經(jīng)添加到Launcher的AppWidget列表，依次向這個(gè)Widget發(fā)出APPWIDGET_ENABLED和 APPWIDGET_UPDATE更新廣播，根據(jù)配置的更新間隔定時(shí)發(fā)出更新廣播。
2. 每個(gè)AppWidget接收到廣播后都會(huì)調(diào)用onEnabled()方法和onUpdate()方法，在onEnabled()方法中進(jìn)行一些初始化操作，在onUpdate()方法中創(chuàng)建RemoteViews布局對(duì)象并通過AppWidgetManager的updateAppWidget(int appWidgetId, RemoteViews remoteViews)方法通知AppWidgetService對(duì)象用RemoteViews對(duì)象更新appWidgetId所對(duì)應(yīng)的AppWidget。
3. AppWidgetService接收到了appWidgetId和RemoteViews后，通過appWidgetId查找已經(jīng)被添加到Launcher的LauncherAppWidgetHostView布局對(duì)象，并RemoteViews中的布局更新到LauncherAppWidgetHostView布局對(duì)象中。AppWidget顯示在Launcher中。

二、AppWidget 預(yù)覽界面的加載流程

1. 操作流程

image.png

如圖，長(zhǎng)按空白區(qū)域出現(xiàn)彈框 ，點(diǎn)擊 widgets選選項(xiàng) 進(jìn)入下圖 widget預(yù)覽頁面

image.png

2. 顯示流程源碼分析

1. Workspace 的構(gòu)造方法中 設(shè)置了 setOnTouchListener 交給 WorkspaceTouchListener類處理

 public Workspace(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        mLauncher = Launcher.getLauncher(context);
        ....
        //設(shè)置 觸摸事件
        setOnTouchListener(new WorkspaceTouchListener(mLauncher, this));
    }

public class WorkspaceTouchListener implements OnTouchListener, Runnable {
    ...
}

2. WorkspaceTouchListener 中的 onTouch 中的 mWorkspace.postDelayed(this, getLongPressTimeout()); 自己實(shí)現(xiàn)的 Runnable接口再觀其 run() 方法。

public boolean onTouch(View view, MotionEvent ev) {
        int action = ev.getActionMasked();
        if (action == ACTION_DOWN) {
            // Check if we can handle long press.
            boolean handleLongPress = canHandleLongPress();

            ...

            cancelLongPress();
            if (handleLongPress) {
                mLongPressState = STATE_REQUESTED;
                mTouchDownPoint.set(ev.getX(), ev.getY());
                  
                // 長(zhǎng)按點(diǎn)擊事件 
                mWorkspace.postDelayed(this, getLongPressTimeout());
            }

            mWorkspace.onTouchEvent(ev);
            // Return true to keep receiving touch events
            return true;
        }
       ......
    }

public void run() {
        if (mLongPressState == STATE_REQUESTED) {
            if (canHandleLongPress()) {
                ...
               
                OptionsPopupView.showDefaultOptions(mLauncher, mTouchDownPoint.x, mTouchDownPoint.y);

            } else {
                cancelLongPress();
            }
        }
    }

3. OptionsPopupView 中添加選項(xiàng)，根據(jù)觸摸坐標(biāo)設(shè)置顯示的區(qū)域 RectF， 最后顯示彈框

public static void showDefaultOptions(Launcher launcher, float x, float y) {
        float halfSize = launcher.getResources().getDimension(R.dimen.options_menu_thumb_size) / 2;
        if (x < 0 || y < 0) {
            x = launcher.getDragLayer().getWidth() / 2;
            y = launcher.getDragLayer().getHeight() / 2;
        }
        RectF target = new RectF(x - halfSize, y - halfSize, x + halfSize, y + halfSize);

        ArrayList<OptionItem> options = new ArrayList<>();
        options.add(new OptionItem(R.string.wallpaper_button_text, R.drawable.ic_wallpaper,
                ControlType.WALLPAPER_BUTTON, OptionsPopupView::startWallpaperPicker));
        options.add(new OptionItem(R.string.widget_button_text, R.drawable.ic_widget,
                ControlType.WIDGETS_BUTTON, OptionsPopupView::onWidgetsClicked));
        options.add(new OptionItem(R.string.settings_button_text, R.drawable.ic_setting,
                ControlType.SETTINGS_BUTTON, OptionsPopupView::startSettings));

        show(launcher, target, options);
    }

 public static void show(Launcher launcher, RectF targetRect, List<OptionItem> items) {
        OptionsPopupView popup = (OptionsPopupView) launcher.getLayoutInflater()
                .inflate(R.layout.longpress_options_menu, launcher.getDragLayer(), false);
        popup.mTargetRect = targetRect;

        for (OptionItem item : items) {
            DeepShortcutView view = popup.inflateAndAdd(R.layout.system_shortcut, popup);
            view.getIconView().setBackgroundResource(item.mIconRes);
            view.getBubbleText().setText(item.mLabelRes);
            view.setDividerVisibility(View.INVISIBLE);
            view.setOnClickListener(popup);
            view.setOnLongClickListener(popup);
            popup.mItemMap.put(view, item);
        }
        popup.reorderAndShow(popup.getChildCount());
    }

4. 其中注意 OptionsPopupView::onWidgetsClicked 這個(gè)是 點(diǎn)擊事件 顯示 WidgetsFullSheet（widget的預(yù)覽界面）

public static boolean onWidgetsClicked(View view) {
        Launcher launcher = Launcher.getLauncher(view.getContext());
        if (launcher.getPackageManager().isSafeMode()) {
            Toast.makeText(launcher, R.string.safemode_widget_error, Toast.LENGTH_SHORT).show();
            return false;
        } else {
            WidgetsFullSheet.show(launcher, true /* animated */);
            return true;
        }
    }

 public static WidgetsFullSheet show(Launcher launcher, boolean animate) {
        WidgetsFullSheet sheet = (WidgetsFullSheet) launcher.getLayoutInflater()
                .inflate(R.layout.widgets_full_sheet, launcher.getDragLayer(), false);
        sheet.mIsOpen = true;
        launcher.getDragLayer().addView(sheet);
        sheet.open(animate);
        return sheet;
    }

二、AppWidget 綁定流程

1. Launcher 的 onCreate 方法中 mModel.startLoader(currentScreen)

 protected void onCreate(Bundle savedInstanceState) {
      ...
       if (!mModel.startLoader(currentScreen)) {
            if (!internalStateHandled) {
                // If we are not binding synchronously, show a fade in animation when
                // the first page bind completes.
                mDragLayer.getAlphaProperty(ALPHA_INDEX_LAUNCHER_LOAD).setValue(0);
            }
        } else {
            // Pages bound synchronously.
            mWorkspace.setCurrentPage(currentScreen);

            setWorkspaceLoading(true);
        }
      ...
}

2. LauncherModel類中 startLoader 方法中 主要關(guān)注 loaderResults.bindWidgets() ，其通過
   callbacks.bindAllWidgets(widgets) ，回調(diào)到 Launcher的bindAllWidgets 方法處理。

 public boolean startLoader(int synchronousBindPage) {
        // Enable queue before starting loader. It will get disabled in Launcher#finishBindingItems
        InstallShortcutReceiver.enableInstallQueue(InstallShortcutReceiver.FLAG_LOADER_RUNNING);
        synchronized (mLock) {
            // Don't bother to start the thread if we know it's not going to do anything
            if (mCallbacks != null && mCallbacks.get() != null) {
                final Callbacks oldCallbacks = mCallbacks.get();
                // Clear any pending bind-runnables from the synchronized load process.
                mUiExecutor.execute(oldCallbacks::clearPendingBinds);

                // If there is already one running, tell it to stop.
                stopLoader();
                LoaderResults loaderResults = new LoaderResults(mApp, sBgDataModel,
                        mBgAllAppsList, synchronousBindPage, mCallbacks);
                if (mModelLoaded && !mIsLoaderTaskRunning) {
                    // Divide the set of loaded items into those that we are binding synchronously,
                    // and everything else that is to be bound normally (asynchronously).
                    loaderResults.bindWorkspace();
                    // For now, continue posting the binding of AllApps as there are other
                    // issues that arise from that.
                    loaderResults.bindAllApps();
                    loaderResults.bindDeepShortcuts();
                    loaderResults.bindWidgets();
                    return true;
                } else {
                  // 其中方法，最后也是走到了  loaderResults.bindWidgets();
                    startLoaderForResults(loaderResults);
                }
            }
        }
        return false;
    }

獲取 widget數(shù)據(jù) 回調(diào)到 launcher中

public void bindWidgets() {
        final ArrayList<WidgetListRowEntry> widgets =
                mBgDataModel.widgetsModel.getWidgetsList(mApp.getContext());
        Runnable r = new Runnable() {
            public void run() {
                Callbacks callbacks = mCallbacks.get();
                if (callbacks != null) {
                    callbacks.bindAllWidgets(widgets);
                }
            }
        };
        mUiExecutor.execute(r);
    }

3. 向 PopupDataProvider類中設(shè)置 widget 數(shù)據(jù)，調(diào)用 AbstractFloatingView.onWidgetsBound();

  Launcher.java

    @Override
    public void bindAllWidgets(final ArrayList<WidgetListRowEntry> allWidgets) {
        mPopupDataProvider.setAllWidgets(allWidgets);
        AbstractFloatingView topView = AbstractFloatingView.getTopOpenView(this);
        if (topView != null) {
            topView.onWidgetsBound();
        }
    }

前面也講到過 widget的預(yù)覽視圖由 WidgetsFullSheet 顯示 而WidgetsFullSheet是 AbstractFloatingView的子類，所以最終調(diào)用了WidgetsFullSheet.onWidgetsBound()。

image.png

WidgetsFullSheet.java

 @Override
    protected void onWidgetsBound() {
      // 從PopupDataProvider類中取出之前設(shè)置進(jìn)去的數(shù)據(jù)，填充adapter
        mAdapter.setWidgets(mLauncher.getPopupDataProvider().getAllWidgets());
    }

4. 總結(jié)上面，widget數(shù)據(jù)最終 交由 WidgetsFullSheet 類處理，下面我們看下

/**
 * Popup for showing the full list of available widgets
 */
public class WidgetsFullSheet extends BaseWidgetSheet
        implements Insettable, ProviderChangedListener {

    private static final long DEFAULT_OPEN_DURATION = 267;
    private static final long FADE_IN_DURATION = 150;
    private static final float VERTICAL_START_POSITION = 0.3f;

    private final Rect mInsets = new Rect();

    private final WidgetsListAdapter mAdapter;

    private WidgetsRecyclerView mRecyclerView;

    public WidgetsFullSheet(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        LauncherAppState apps = LauncherAppState.getInstance(context);
        mAdapter = new WidgetsListAdapter(context,
                LayoutInflater.from(context), apps.getWidgetCache(), apps.getIconCache(),
                this, this);

    }

    public WidgetsFullSheet(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        mContent = findViewById(R.id.container);

        mRecyclerView = findViewById(R.id.widgets_list_view);
        mRecyclerView.setAdapter(mAdapter);
        mAdapter.setApplyBitmapDeferred(true, mRecyclerView);

        TopRoundedCornerView springLayout = (TopRoundedCornerView) mContent;
        springLayout.addSpringView(R.id.widgets_list_view);
        mRecyclerView.setEdgeEffectFactory(springLayout.createEdgeEffectFactory());
        onWidgetsBound();
    }

    @Override
    protected Pair<View, String> getAccessibilityTarget() {
        return Pair.create(mRecyclerView, getContext().getString(
                mIsOpen ? R.string.widgets_list : R.string.widgets_list_closed));
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        mLauncher.getAppWidgetHost().addProviderChangeListener(this);
        notifyWidgetProvidersChanged();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        mLauncher.getAppWidgetHost().removeProviderChangeListener(this);
    }

    @Override
    public void setInsets(Rect insets) {
        mInsets.set(insets);

        mRecyclerView.setPadding(
                mRecyclerView.getPaddingLeft(), mRecyclerView.getPaddingTop(),
                mRecyclerView.getPaddingRight(), insets.bottom);
        if (insets.bottom > 0) {
            setupNavBarColor();
        } else {
            clearNavBarColor();
        }

        ((TopRoundedCornerView) mContent).setNavBarScrimHeight(mInsets.bottom);
        requestLayout();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthUsed;
        if (mInsets.bottom > 0) {
            widthUsed = 0;
        } else {
            Rect padding = mLauncher.getDeviceProfile().workspacePadding;
            widthUsed = Math.max(padding.left + padding.right,
                    2 * (mInsets.left + mInsets.right));
        }

        int heightUsed = mInsets.top + mLauncher.getDeviceProfile().edgeMarginPx;
        measureChildWithMargins(mContent, widthMeasureSpec,
                widthUsed, heightMeasureSpec, heightUsed);
        setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
                MeasureSpec.getSize(heightMeasureSpec));
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int width = r - l;
        int height = b - t;

        // Content is laid out as center bottom aligned
        int contentWidth = mContent.getMeasuredWidth();
        int contentLeft = (width - contentWidth) / 2;
        mContent.layout(contentLeft, height - mContent.getMeasuredHeight(),
                contentLeft + contentWidth, height);

        setTranslationShift(mTranslationShift);
    }

    @Override
    public void notifyWidgetProvidersChanged() {
        mLauncher.refreshAndBindWidgetsForPackageUser(null);
    }

    @Override
    protected void onWidgetsBound() {
        mAdapter.setWidgets(mLauncher.getPopupDataProvider().getAllWidgets());
    }

    private void open(boolean animate) {
        if (animate) {
            if (mLauncher.getDragLayer().getInsets().bottom > 0) {
                mContent.setAlpha(0);
                setTranslationShift(VERTICAL_START_POSITION);
            }
            mOpenCloseAnimator.setValues(
                    PropertyValuesHolder.ofFloat(TRANSLATION_SHIFT, TRANSLATION_SHIFT_OPENED));
            mOpenCloseAnimator
                    .setDuration(DEFAULT_OPEN_DURATION)
                    .setInterpolator(AnimationUtils.loadInterpolator(
                            getContext(), android.R.interpolator.linear_out_slow_in));
            mOpenCloseAnimator.addListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mRecyclerView.setLayoutFrozen(false);
                    mAdapter.setApplyBitmapDeferred(false, mRecyclerView);
                    mOpenCloseAnimator.removeListener(this);
                }
            });
            post(() -> {
                mRecyclerView.setLayoutFrozen(true);
                mOpenCloseAnimator.start();
                mContent.animate().alpha(1).setDuration(FADE_IN_DURATION);
            });
        } else {
            setTranslationShift(TRANSLATION_SHIFT_OPENED);
            mAdapter.setApplyBitmapDeferred(false, mRecyclerView);
            post(this::announceAccessibilityChanges);
        }
    }

    @Override
    protected void handleClose(boolean animate) {
        handleClose(animate, DEFAULT_OPEN_DURATION);
    }

    @Override
    protected boolean isOfType(int type) {
        return (type & TYPE_WIDGETS_FULL_SHEET) != 0;
    }

    @Override
    public boolean onControllerInterceptTouchEvent(MotionEvent ev) {
        // Disable swipe down when recycler view is scrolling
        if (ev.getAction() == MotionEvent.ACTION_DOWN) {
            mNoIntercept = false;
            RecyclerViewFastScroller scroller = mRecyclerView.getScrollbar();
            if (scroller.getThumbOffsetY() >= 0 &&
                    mLauncher.getDragLayer().isEventOverView(scroller, ev)) {
                mNoIntercept = true;
            } else if (mLauncher.getDragLayer().isEventOverView(mContent, ev)) {
                mNoIntercept = !mRecyclerView.shouldContainerScroll(ev, mLauncher.getDragLayer());
            }
        }
        return super.onControllerInterceptTouchEvent(ev);
    }

    public static WidgetsFullSheet show(Launcher launcher, boolean animate) {
        WidgetsFullSheet sheet = (WidgetsFullSheet) launcher.getLayoutInflater()
                .inflate(R.layout.widgets_full_sheet, launcher.getDragLayer(), false);
        sheet.mIsOpen = true;
        launcher.getDragLayer().addView(sheet);
        sheet.open(animate);
        return sheet;
    }

    @Override
    protected int getElementsRowCount() {
        return mAdapter.getItemCount();
    }
}

由以上代碼可以看出 WidgetsFullSheet 是一個(gè)自定義的view ，構(gòu)造方法中 mAdapter = new WidgetsListAdapter(); 在show(Launcher launcher, boolean animate) 方法中 inflate(R.layout.widgets_full_sheet，，) 布局文件;在 onFinishInflate() 方法中 mRecyclerView = findViewById(R.id.widgets_list_view)； mRecyclerView.setAdapter(mAdapter); 最后由之前所說的
onWidgetsBound() 方法中 adapter 設(shè)置數(shù)據(jù)。

R.layout.widgets_full_sheet 文件

<com.android.launcher3.widget.WidgetsFullSheet
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:theme="?attr/widgetsTheme" >

    <com.android.launcher3.views.TopRoundedCornerView
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="?android:attr/colorPrimary"
        android:elevation="4dp">

        <com.android.launcher3.widget.WidgetsRecyclerView
            android:id="@+id/widgets_list_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:clipToPadding="false" />

        <!-- Fast scroller popup -->
        <TextView
            android:id="@+id/fast_scroller_popup"
            style="@style/FastScrollerPopup"
            android:layout_alignParentEnd="true"
            android:layout_alignParentTop="true"
            android:layout_marginEnd="@dimen/fastscroll_popup_margin" />

        <com.android.launcher3.views.RecyclerViewFastScroller
            android:id="@+id/fast_scroller"
            android:layout_width="@dimen/fastscroll_width"
            android:layout_height="match_parent"
            android:layout_alignParentEnd="true"
            android:layout_alignParentTop="true"
            android:layout_marginEnd="@dimen/fastscroll_end_margin" />
    </com.android.launcher3.views.TopRoundedCornerView>
</com.android.launcher3.widget.WidgetsFullSheet>

5. WidgetsListAdapter 就是一個(gè)recycleView的adapter ，onCreateViewHolder()中
   inflate(R.layout.widgets_list_row_view, parent, false) 布局文件如下

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:launcher="http://schemas.android.com/apk/res-auto"
    android:id="@+id/widgets_cell_list_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:focusable="true"
    android:descendantFocusability="afterDescendants">

    <!-- Section info -->

    <com.android.launcher3.BubbleTextView
        android:id="@+id/section"
        android:layout_width="match_parent"
        android:layout_height="@dimen/widget_section_height"
        android:background="?android:attr/colorPrimary"
        android:drawablePadding="@dimen/widget_section_horizontal_padding"
        android:focusable="true"
        android:gravity="start|center_vertical"
        android:paddingBottom="@dimen/widget_section_vertical_padding"
        android:paddingLeft="@dimen/widget_section_horizontal_padding"
        android:paddingRight="@dimen/widget_section_horizontal_padding"
        android:paddingTop="@dimen/widget_section_vertical_padding"
        android:singleLine="true"
        android:textColor="?android:attr/textColorPrimary"
        android:textSize="16sp"
        android:textAlignment="viewStart"
        launcher:iconDisplay="widget_section"
        launcher:iconSizeOverride="@dimen/widget_section_icon_size"
        launcher:layoutHorizontal="true" />

    <include layout="@layout/widgets_scroll_container" />
</LinearLayout>

widgets_scroll_container.xml 文件

<HorizontalScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/widgets_scroll_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?android:attr/colorPrimaryDark"
    android:scrollbars="none">
    <LinearLayout
        android:id="@+id/widgets_cell_list"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingStart="0dp"
        android:paddingEnd="0dp"
        android:orientation="horizontal"
        android:showDividers="none"/>
</HorizontalScrollView>

然后 看 onBindViewHolder 方法

@Override
    public void onBindViewHolder(WidgetsRowViewHolder holder, int pos) {
        WidgetListRowEntry entry = mEntries.get(pos);
        List<WidgetItem> infoList = entry.widgets;

        ViewGroup row = holder.cellContainer;
        if (DEBUG) {
            Log.d(TAG, String.format(
                    "onBindViewHolder [pos=%d, widget#=%d, row.getChildCount=%d]",
                    pos, infoList.size(), row.getChildCount()));
        }

        // Add more views.
        // if there are too many, hide them.
        int expectedChildCount = infoList.size() + Math.max(0, infoList.size() - 1);
        int childCount = row.getChildCount();

        if (expectedChildCount > childCount) {
            for (int i = childCount ; i < expectedChildCount; i++) {
                if ((i & 1) == 1) {
                    // Add a divider for odd index
                    mLayoutInflater.inflate(R.layout.widget_list_divider, row);
                } else {
                    // Add cell for even index
                    WidgetCell widget = (WidgetCell) mLayoutInflater.inflate(
                            R.layout.widget_cell, row, false);

                    // set up touch.
                    widget.setOnClickListener(mIconClickListener);
                    widget.setOnLongClickListener(mIconLongClickListener);
                    row.addView(widget);
                }
            }
        } else if (expectedChildCount < childCount) {
            for (int i = expectedChildCount ; i < childCount; i++) {
                row.getChildAt(i).setVisibility(View.GONE);
            }
        }

        // Bind the views in the application info section.
        holder.title.applyFromPackageItemInfo(entry.pkgItem);

        // Bind the view in the widget horizontal tray region.
        for (int i=0; i < infoList.size(); i++) {
            WidgetCell widget = (WidgetCell) row.getChildAt(2*i);
            widget.applyFromCellItem(infoList.get(i), mWidgetPreviewLoader);
            widget.setApplyBitmapDeferred(mApplyBitmapDeferred);
            widget.ensurePreview();
            widget.setVisibility(View.VISIBLE);

            if (i > 0) {
                row.getChildAt(2*i - 1).setVisibility(View.VISIBLE);
            }
        }
    }

以單個(gè)應(yīng)用進(jìn)行分組 作為一級(jí)菜單，一個(gè)應(yīng)用可能多個(gè) wideget 作為二級(jí)菜單，用WidgetCell作為容器放置于HorizontalScrollView中 橫向滾動(dòng)；for 循環(huán)中 獲取每一個(gè)WidgetCell調(diào)用applyFromCellItem() 和 ensurePreview() 。

6. WidgetCell 作為單個(gè)widget顯示的容器，applyFromCellItem（）設(shè)置數(shù)據(jù)，ensurePreview（）中加載預(yù)覽圖

   
   
   image.png

    public void applyFromCellItem(WidgetItem item, WidgetPreviewLoader loader) {
        mItem = item;
        mWidgetName.setText(mItem.label);
        mWidgetDims.setText(getContext().getString(R.string.widget_dims_format,
                mItem.spanX, mItem.spanY));
        mWidgetDims.setContentDescription(getContext().getString(
                R.string.widget_accessible_dims_format, mItem.spanX, mItem.spanY));
        mWidgetPreviewLoader = loader;

        if (item.activityInfo != null) {
            setTag(new PendingAddShortcutInfo(item.activityInfo));
        } else {
            setTag(new PendingAddWidgetInfo(item.widgetInfo));
        }
    }

 public void ensurePreview() {
        if (mActiveRequest != null) {
            return;
        }
        mActiveRequest = mWidgetPreviewLoader.getPreview(
                mItem, mPresetPreviewSize, mPresetPreviewSize, this);
    }

7. 其中 預(yù)覽圖 交由WidgetPreviewLoader類中處理 ,其中PreviewLoadTask 是一個(gè) AsyncTask ,從緩存池中獲取 空白的bitmap ，從數(shù)據(jù)庫中獲取預(yù)覽圖數(shù)據(jù) 賦值給 空白的bitmap ，最后調(diào)用 mCaller.applyPreview(preview);

   public CancellationSignal getPreview(WidgetItem item, int previewWidth,
            int previewHeight, WidgetCell caller) {
        String size = previewWidth + "x" + previewHeight;
        WidgetCacheKey key = new WidgetCacheKey(item.componentName, item.user, size);

        PreviewLoadTask task = new PreviewLoadTask(key, item, previewWidth, previewHeight, caller);
        task.executeOnExecutor(Utilities.THREAD_POOL_EXECUTOR);

        CancellationSignal signal = new CancellationSignal();
        signal.setOnCancelListener(task);
        return signal;
    }

public class PreviewLoadTask extends AsyncTask<Void, Void, Bitmap>
            implements CancellationSignal.OnCancelListener {
        @Thunk final WidgetCacheKey mKey;
        private final WidgetItem mInfo;
        private final int mPreviewHeight;
        private final int mPreviewWidth;
        private final WidgetCell mCaller;
        private final BaseActivity mActivity;
        @Thunk long[] mVersions;
        @Thunk Bitmap mBitmapToRecycle;

        PreviewLoadTask(WidgetCacheKey key, WidgetItem info, int previewWidth,
                int previewHeight, WidgetCell caller) {
            mKey = key;
            mInfo = info;
            mPreviewHeight = previewHeight;
            mPreviewWidth = previewWidth;
            mCaller = caller;
            mActivity = BaseActivity.fromContext(mCaller.getContext());
            if (DEBUG) {
                Log.d(TAG, String.format("%s, %s, %d, %d",
                        mKey, mInfo, mPreviewHeight, mPreviewWidth));
            }
        }

        @Override
        protected Bitmap doInBackground(Void... params) {
            Bitmap unusedBitmap = null;

            // If already cancelled before this gets to run in the background, then return early
            if (isCancelled()) {
                return null;
            }
            synchronized (mUnusedBitmaps) {
                // Check if we can re-use a bitmap
                for (Bitmap candidate : mUnusedBitmaps) {
                    if (candidate != null && candidate.isMutable() &&
                            candidate.getWidth() == mPreviewWidth &&
                            candidate.getHeight() == mPreviewHeight) {
                        unusedBitmap = candidate;
                        mUnusedBitmaps.remove(unusedBitmap);
                        break;
                    }
                }
            }

            // creating a bitmap is expensive. Do not do this inside synchronized block.
            if (unusedBitmap == null) {
                unusedBitmap = Bitmap.createBitmap(mPreviewWidth, mPreviewHeight, Config.ARGB_8888);
            }
            // If cancelled now, don't bother reading the preview from the DB
            if (isCancelled()) {
                return unusedBitmap;
            }
            Bitmap preview = readFromDb(mKey, unusedBitmap, this);
            // Only consider generating the preview if we have not cancelled the task already
            if (!isCancelled() && preview == null) {
                // Fetch the version info before we generate the preview, so that, in-case the
                // app was updated while we are generating the preview, we use the old version info,
                // which would gets re-written next time.
                boolean persistable = mInfo.activityInfo == null
                        || mInfo.activityInfo.isPersistable();
                mVersions = persistable ? getPackageVersion(mKey.componentName.getPackageName())
                        : null;

                // it's not in the db... we need to generate it
                preview = generatePreview(mActivity, mInfo, unusedBitmap, mPreviewWidth, mPreviewHeight);
            }
            return preview;
        }

        @Override
        protected void onPostExecute(final Bitmap preview) {
            mCaller.applyPreview(preview);

            // Write the generated preview to the DB in the worker thread
            if (mVersions != null) {
                mWorkerHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        if (!isCancelled()) {
                            // If we are still using this preview, then write it to the DB and then
                            // let the normal clear mechanism recycle the bitmap
                            writeToDb(mKey, mVersions, preview);
                            mBitmapToRecycle = preview;
                        } else {
                            // If we've already cancelled, then skip writing the bitmap to the DB
                            // and manually add the bitmap back to the recycled set
                            synchronized (mUnusedBitmaps) {
                                mUnusedBitmaps.add(preview);
                            }
                        }
                    }
                });
            } else {
                // If we don't need to write to disk, then ensure the preview gets recycled by
                // the normal clear mechanism
                mBitmapToRecycle = preview;
            }
        }

        @Override
        protected void onCancelled(final Bitmap preview) {
            // If we've cancelled while the task is running, then can return the bitmap to the
            // recycled set immediately. Otherwise, it will be recycled after the preview is written
            // to disk.
            if (preview != null) {
                mWorkerHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        synchronized (mUnusedBitmaps) {
                            mUnusedBitmaps.add(preview);
                        }
                    }
                });
            }
        }

        @Override
        public void onCancel() {
            cancel(true);

            // This only handles the case where the PreviewLoadTask is cancelled after the task has
            // successfully completed (including having written to disk when necessary).  In the
            // other cases where it is cancelled while the task is running, it will be cleaned up
            // in the tasks's onCancelled() call, and if cancelled while the task is writing to
            // disk, it will be cancelled in the task's onPostExecute() call.
            if (mBitmapToRecycle != null) {
                mWorkerHandler.post(new Runnable() {
                    @Override
                    public void run() {
                        synchronized (mUnusedBitmaps) {
                            mUnusedBitmaps.add(mBitmapToRecycle);
                        }
                        mBitmapToRecycle = null;
                    }
                });
            }
        }
    }

 public void applyPreview(Bitmap bitmap) {
        if (mApplyBitmapDeferred) {
            mDeferredBitmap = bitmap;
            return;
        }
        if (bitmap != null) {
            mWidgetImage.setBitmap(bitmap,
                    DrawableFactory.get(getContext()).getBadgeForUser(mItem.user, getContext()));
            if (mAnimatePreview) {
                mWidgetImage.setAlpha(0f);
                ViewPropertyAnimator anim = mWidgetImage.animate();
                anim.alpha(1.0f).setDuration(FADE_IN_DURATION_MS);
            } else {
                mWidgetImage.setAlpha(1f);
            }
        }
    }

自此，整個(gè) widget的 預(yù)覽列表數(shù)據(jù)加載完成。