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Android关于Blockly对Workspace中的block数据保存及读取的流程，及改造原生代码实现Trash垃圾桶中的block保存及读取

分类: 文章 • 2022-11-01 17:35:42

一.Blockly对Workspace中的block数据保存及读取的流程源码分析：

 1.Workspace的自动保存：在AbstractBlocklyActivity中
有onAutosave()的方法用于对Workspace的block数据进行保存。保存的流程如下

  1).在AbstractBlocklyActivity的onAutosave()，获取自动保存的路径：

/**
 * Called when an autosave of the workspace is triggered, typically by {@link #onPause()}.
 * By default this saves the workspace to a file in the app's directory.
 */
protected void onAutosave() {
    try {
        mBlocklyActivityHelper.saveWorkspaceToAppDir(getWorkspaceAutosavePath()); //获取自动保存Workspace的block数据的路径
    } catch (FileNotFoundException | BlocklySerializerException e) {
        Log.e(TAG, "Failed to autosaving workspace.", e);
    }
}

  2).
在BlocklyActivityHelper中获取到Wrokspace的对象对传入的文件路径，进行serialToXml序列化到xml的操作：

/**
 * Save the workspace to the given file in the application's private data directory, and show a
 * status toast. If the save fails, the error is logged.
 */
public void saveWorkspaceToAppDir(String filename)
        throws FileNotFoundException, BlocklySerializerException{
    Workspace workspace = mWorkspaceFragment.getWorkspace();
    workspace.serializeToXml(mActivity.openFileOutput(filename, Context.MODE_PRIVATE)); //将Workspace的数据序列化到xml文件保存
}

  3).在Workspace中能获取到画布中的block的集合mRootBlocks，最终把这mRootBlocks和文件路径交给BlocklyXmlHelper

实现具体的数据序列化到XML中保存：

/**
 * Outputs the workspace as an XML string.
 *
 * @param os The output stream to write to.
 * @throws BlocklySerializerException if there was a failure while serializing.
 */
public void serializeToXml(OutputStream os) throws BlocklySerializerException {
    BlocklyXmlHelper.writeToXml(mRootBlocks, os, IOOptions.WRITE_ALL_DATA);//在拖Workspace的mRootBlocks的block写到xml文件中，mRootBlocks即是连接到画布中的block块的集合
}

 4).BlocklyXmlHelper具体到把每个block块的数据以tag的形式存在xml中：

/**
 * Serializes all Blocks in the given list and writes them to the given output stream.
 *
 * @param toSerialize A list of Blocks to serialize.
 * @param os An OutputStream to write the blocks to.
 * @param options The options to configure the block serialization. If omitted,
 *                {@link IOOptions#WRITE_ALL_DATA} will be used by default.
 *
 * @throws BlocklySerializerException
 */
public static void writeToXml(@NonNull List<Block> toSerialize, @NonNull OutputStream os,
                              @Nullable IOOptions options)
        throws BlocklySerializerException {
    writeToXmlImpl(toSerialize, os, null, options);
}

/**
 * Serializes all Blocks in the given list and writes them to the either the output stream or
 * writer, whichever is not null.
 *
 * @param toSerialize A list of Blocks to serialize.
 * @param os An OutputStream to write the blocks to.
 * @param writer A writer to write the blocks to, if {@code os} is null.
 * @param options The options to configure the block serialization. If omitted,
 *                {@link IOOptions#WRITE_ALL_DATA} will be used by default.
 *
 * @throws BlocklySerializerException
 */
public static void writeToXmlImpl(final @NonNull List<Block> toSerialize,
                                  @Nullable OutputStream os, @Nullable Writer writer,
                                  @Nullable IOOptions options)
        throws BlocklySerializerException {
    final IOOptions finalOptions = options == null ? IOOptions.WRITE_ALL_DATA : options;
    XmlContentWriter contentWriter = new XmlContentWriter() {
        @Override
        public void write(XmlSerializer serializer) throws IOException {
            serializer.setPrefix("", XML_NAMESPACE);
            serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);

            serializer.startTag(XML_NAMESPACE, "xml");
            for (int i = 0; i < toSerialize.size(); i++) {      //遍历每个block块以tag的形式存在xml中
                toSerialize.get(i).serialize(serializer, true, finalOptions);
            }
            serializer.endTag(XML_NAMESPACE, "xml");
        }
    };
    try {
        if (os != null) {
            writeXml(os, contentWriter);
        } else {
            writeXml(writer, contentWriter);
        }
    } catch (IOException e) {
        throw new BlocklySerializerException(e);
    }
}

以上就是Workspace中的block自动保存的流程。

 2.Workspace的自动加载：在AbstractBlocklyActivity中有onAutoload()的方法用于对保存在xml里Workspace的block数据

读取并加载显示到Workspace。保存的流程如下

  1).在AbstractBlocklyActivity的onAutoload()，获取自动保存的路径把路径传给BlocklyActivityHelper：

/**
 * Called when the activity tries to restore the autosaved workspace, typically by
 * {@link #onCreate(Bundle)} if there was no workspace data in the bundle.
 *
 * @return true if a previously saved workspace was loaded, false otherwise.
 */
protected boolean onAutoload() {
    String filePath = getWorkspaceAutosavePath();
    try {
        mBlocklyActivityHelper.loadWorkspaceFromAppDir(filePath);
        return true;
    } catch (FileNotFoundException e) {
        // No workspace was saved previously.
    } catch (BlockLoadingException | IOException e) {
        Log.e(TAG, "Failed to load workspace", e);
        mBlocklyActivityHelper.getController().resetWorkspace();

        File file = getFileStreamPath(filePath);
        if (!file.delete()) {
            Log.e(TAG, "Failed to delete corrupted autoload workspace: " + filePath);
        }
    }
    return false;
}

 2).BlocklyActivityHelper获取到BlocklyController的实例接收自动保存的路径：

/**
 * Loads the workspace from the given file in the application's private data directory.
 * @param filename The path to the file, in the application's local storage.
 * @throws IOException If there is a underlying problem with the input.
 * @throws BlockLoadingException If there is a error with the workspace XML format or blocks.
 */
public void loadWorkspaceFromAppDir(String filename) throws IOException, BlockLoadingException {
    mController.loadWorkspaceContents(mActivity.openFileInput(filename));      //把路径传到BlocklyController
}

3).BlocklyController中操作Workspace读取数据并显示把数据转成block显示在画布中：

/**
 * Reads the workspace in from a XML stream. This will clear the workspace and replace it with
 * the contents of the xml.
 *
 * @param workspaceXmlStream The input stream to read from.
 * @return True if successful. Otherwise, false with error logged.
 */
public void loadWorkspaceContents(InputStream workspaceXmlStream) throws BlockLoadingException {
    mWorkspace.loadWorkspaceContents(workspaceXmlStream);   //在Workspace读取保存的数据
    initBlockViews();   //初始化所读取到的block数据显示在画布中
}

4).在保存的流程可以知道，Workspace是保存中数据的源头，同样是读取加载数据后显示的源头：

/**
 * Reads the workspace in from a XML stream. This will clear the workspace and replace it with
 * the contents of the xml.
 *
 * @param is The input stream to read from.
 * @throws BlockLoadingException If workspace was not loaded. May wrap an IOException or another
 *                               BlockLoadingException.
 */
public void loadWorkspaceContents(InputStream is) throws BlockLoadingException {
    List<Block> newBlocks = BlocklyXmlHelper.loadFromXml(is, mBlockFactory);    //读取自动保存数据转成block的集合

    // Successfully deserialized.  Update workspace.
    // TODO: (#22) Add proper variable support.
    // For now just save and restore the list of variables.
    Set<String> vars = mVariableNameManager.getUsedNames();
    mController.resetWorkspace();
    for (String varName : vars) {
        mController.addVariable(varName);
    }

    mRootBlocks.addAll(newBlocks);      //将加载的block的集合加载到mRootBlocks
    mStats.collectStats(newBlocks, true /* recursive */);
}

5).Workspace中block数据的保存和读取都是转交给BlocklyXmlHelper进行具体的数据的序列化操作的：

/**
 * Convenience function that creates a new {@link ArrayList}.
 * @param inputXml The input stream of XML from which to read.
 * @throws BlockLoadingException If any error occurs with the input. It may wrap an IOException
 *                               or XmlPullParserException as a root cause.
 */
public static List<Block> loadFromXml(InputStream inputXml, BlockFactory blockFactory)
        throws BlockLoadingException {
    List<Block> result = new ArrayList<>();
    loadBlocksFromXml(inputXml, null, blockFactory, result);
    return result;
}

保存的xml数据解析成一个个的block块：

/**
 * Loads a list of top-level Blocks from XML.  Each top-level Block may have many Blocks
 * contained in it or descending from it.
 *
 * @param inStream The input stream to read blocks from. Maybe null.
 * @param inString The xml string to read blocks from if {@code insStream} is null.
 * @param blockFactory The BlockFactory for the workspace where the Blocks are being loaded.
 * @param result An list (usually empty) to append new top-level Blocks to.
 *
 * @throws BlockLoadingException If any error occurs with the input. It may wrap an IOException
 *                               or XmlPullParserException as a root cause.
 */
private static void loadBlocksFromXml(
        InputStream inStream, String inString, BlockFactory blockFactory, List<Block> result)
        throws BlockLoadingException {
    StringReader reader = null;
    try {
        XmlPullParser parser = PARSER_FACTORY.newPullParser();
        if (LOG_INPUT_XML) {
            if (inStream != null) {
                StringBuilder sb = new StringBuilder();
                BufferedReader br = new BufferedReader(new InputStreamReader(inStream));
                String line = br.readLine();
                while (line != null) {
                    sb.append(line).append('\n');
                    line = br.readLine();
                }
                br.close();
                inStream = null;
                inString = sb.toString();
            }
            Log.d(TAG, "BlocklyXmlHelper.loadBlocksFromXml()\n" + inString);
        }
        if (inStream != null) {
            parser.setInput(inStream, null);
        } else {
            reader = new StringReader(inString);
            parser.setInput(reader);
        }
        int eventType = parser.getEventType();
        while (eventType != XmlPullParser.END_DOCUMENT) {
            switch (eventType) {
                case XmlPullParser.START_TAG:
                    if (parser.getName() == null) {
                        throw new BlockLoadingException("Malformed XML; aborting.");
                    }
                    if (parser.getName().equalsIgnoreCase("block")) {
                        result.add(blockFactory.fromXml(parser));
                    } else if (parser.getName().equalsIgnoreCase("shadow")) {
                        throw new IllegalArgumentException(
                                "Shadow blocks may not be top level blocks.");
                    }
                    break;

                default:
                    break;
            }
            eventType = parser.next();
        }
    } catch (XmlPullParserException | IOException e) {
        throw new BlockLoadingException(e);
    }
    if (reader != null) {
        reader.close();
    }
}

二、对于Trash垃圾桶所涉及的逻辑分析：

 1.如图，是原生Blockly中关于Trash的逻辑。点击Trash垃圾桶就会把用户的删除的block：

Android关于Blockly对Workspace中的block数据保存及读取的流程，及改造原生代码实现Trash垃圾桶中的block保存及读取

 2).接下来分析，Trash中的逻辑是怎么添加到代码中去的，a.首先在AbstractBlocklyFragment依附在

AbstractBlocklyActivity时已经在onCreatView()创建BlocklyActivityHelper，这样就把关于业务逻辑交给了

BlocklyActivityHelper处理；b.接下来在BlocklyActivityHelper的构造方法中初始一系列化的帮助类，实例化帮助类之后

用BlocklyController建造者模式构建出每个模块的UI及业务逻辑处理；c.BlocklyController中管控着所有block的操作，

其下属FlyoutController控制器管控着ToolBox和Trash的界面显示和关闭；d.而本篇博客要分析的Trash垃圾桶Block的数据

的来源最终来自Workspace,存储在Trash垃圾桶Block的数据保存在对象BlocklyCategory里的mItem字段中。

 3).用Blockly的源码来体现2）中描述的逻辑流程：

 a.首先在AbstractBlocklyFragment依附在AbstractBlocklyActivity时已经在onCreatView()创建

BlocklyActivityHelper，这样就把关于业务逻辑交给了BlocklyActivityHelper处理：

/**
 * Creates the activity's views and subfragments (via {@link #onCreateSubViews}, and then
 * initializes Blockly via {@link #onCreateActivityHelper()}, using the values from
 * {@link #getBlockDefinitionsJsonPaths} and {@link #getToolboxContentsXmlPath}.
 * Subclasses should override those methods to configure the Blockly environment.
 * <p/>
 * Once the controller and fragments are configured, if {@link #checkAllowRestoreBlocklyState}
 * returns true, the activity will attempt to load a prior workspace from the instance state
 * bundle.  If no workspace is loaded, it defers to {@link #onLoadInitialWorkspace}.
 */
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
        @Nullable Bundle savedInstanceState) {
    mRootView = onCreateSubViews(inflater);
    //创建AbstractBlocklyFragment时实例化BlocklyActivityHelper，把有关于业务逻辑都交给BlocklyActivityHelper处理
    mBlocklyActivityHelper = onCreateActivityHelper();

    if (mBlocklyActivityHelper == null) {
        throw new IllegalStateException("BlocklyActivityHelper is null. "
                + "onCreateActivityHelper must return a instance.");
    }
    resetBlockFactory();  // Initial load of block definitions, extensions, and mutators.
    configureCategoryFactories();  // After BlockFactory; before Toolbox
    reloadToolbox();

    // Load the workspace.
    boolean loadedPriorInstance = checkAllowRestoreBlocklyState(savedInstanceState)
            && (getController().onRestoreSnapshot(savedInstanceState) || onAutoload());
    if (!loadedPriorInstance) {
        onLoadInitialWorkspace();
    }

    setHasOptionsMenu(true);

    return mRootView;
}

 b.接下来在BlocklyActivityHelper的构造方法中初始一系列化的帮助类，实例化帮助类之后

用BlocklyController建造者模式构建出每个模块的UI及业务逻辑处理：

/**
 * Creates the activity helper and initializes Blockly. Must be called during
 * {@link Activity#onCreate}. Executes the following sequence of calls during initialization:
 * <ul>
 *     <li>{@link #onFindFragments} to find fragments</li>
 *     <li>{@link #onCreateBlockViewFactory}</li>
 * </ul>
 * Subclasses should override those methods to configure the Blockly environment.
 *
 * @throws IllegalStateException If error occurs during initialization. Assumes all initial
 *                               compile-time assets are known to be valid.
 */
public BlocklyActivityHelper(AppCompatActivity activity, FragmentManager fragmentManager) {
    mActivity = activity;

    onFindFragments(fragmentManager);
    if (mWorkspaceFragment == null) {
        throw new IllegalStateException("mWorkspaceFragment is null");
    }
    //初始实例化帮助类
    mWorkspaceHelper = new WorkspaceHelper(activity);
    mBlockViewFactory = onCreateBlockViewFactory(mWorkspaceHelper);
    mClipDataHelper = onCreateClipDataHelper();
    mCodeGeneratorManager = new CodeGeneratorManager(activity);
    //用BlocklyController建造者模式构建出每个模块的UI及业务逻辑处理
    BlocklyController.Builder builder = new BlocklyController.Builder(activity)
            .setClipDataHelper(mClipDataHelper)
            .setWorkspaceHelper(mWorkspaceHelper)
            .setBlockViewFactory(mBlockViewFactory)
            .setWorkspaceFragment(mWorkspaceFragment)
            .setTrashUi(mTrashBlockList)        //设置Trash中的UI及业务逻辑实现
            .setToolboxUi(mToolboxBlockList, mCategoryFragment);
    mController = builder.build();

    onCreateVariableCallback();
    onCreateMutatorListener();

    onConfigureTrashIcon();
    onConfigureZoomInButton();
    onConfigureZoomOutButton();
    onConfigureCenterViewButton();
}

 BlocklyController中建造者模式的构建：

/**
 * Create a new workspace using the configuration in this builder.
 *
 * @return A new {@link BlocklyController}.
 */
public BlocklyController build() {
    if (mViewFactory == null && (mWorkspaceFragment != null || mTrashUi != null
            || mToolbox != null || mCategoryUi != null)) {
        throw new IllegalStateException(
                "BlockViewFactory cannot be null when using UIs.");
    }

    if (mWorkspaceHelper == null) {
        mWorkspaceHelper = new WorkspaceHelper(mContext);
    }

    BlockClipDataHelper blockClipDataHelper = mClipHelper;
    if (blockClipDataHelper == null) {
        blockClipDataHelper = SingleMimeTypeClipDataHelper.getDefault(mContext);
    }

    BlockFactory factory = new BlockFactory();
    loadBlockDefinitionsFromResources(factory, mBlockDefResources);
    loadBlockDefinitionsFromAssets(factory, mBlockDefAssets);
    BlocklyController controller = new BlocklyController(
            mContext, factory, mWorkspaceHelper, blockClipDataHelper, mViewFactory);
    loadToolbox(controller);

    // Any of the following may be null and result in a no-op.
    controller.setWorkspaceFragment(mWorkspaceFragment);
    controller.setTrashUi(mTrashUi);        //在BlocklyController以建造者模式构建的时候设置了Trash垃圾桶的具体逻辑实现
    controller.setToolboxUi(mToolbox, mCategoryUi);
    controller.setTrashIcon(mTrashIcon);
    controller.setVariableCallback(mVariableCallback);

    return controller;
}

 c.BlocklyController中管控着所有block的操作，其下属FlyoutController控制器管控着ToolBox和

Trash的界面显示和关闭：

 BlocklyController的setTrashUi()方法是设置数据的来源：

/**
 * Connects a {@link BlockListUI} for the trash to this controller.
 *
 * @param trashUi
 */
public void setTrashUi(@Nullable BlockListUI trashUi) {
    if (trashUi != null && mViewFactory == null) {
        throw new IllegalStateException("Cannot set UIs without a BlockViewFactory.");
    }
    //BlocklyController中管控着所有Block的操作，其下属FlyoutController控制器管控着
    //ToolBox和Trash能关闭显示的控制
    mFlyoutController.setTrashUi(trashUi);
    //给从Workspace拿到TrashCategory的内容设置到FlyoutController
    mFlyoutController.setTrashContents(mWorkspace.getTrashCategory());
}

 在BlocklyController的setTrashIcon()方法是设置Trash的图标及内部逻辑实现：

/**
 * Assigns the view used for opening/closing the trash.
 *
 * @param trashIcon The trash icon for dropping blocks.
 */
public void setTrashIcon(View trashIcon) {
    //设置Trash的图标及其内部逻辑实现初始化
    mFlyoutController.setTrashIcon(trashIcon);
}

 在FlyoutController的setTrashIcon()设置Trash的打开及关闭的监听：

/**
 * @param trashIcon The view for toggling the trash.
 */
public void setTrashIcon(View trashIcon) {
    if (trashIcon == null) {
        return;
    }
    // The trash icon is always a drop target.
    trashIcon.setOnDragListener(new OnDragToTrashListener(mController));
    if (mTrashUi != null && mTrashIsCloseable) {
        // But we only need a click listener if the trash can be closed.
        trashIcon.setOnClickListener(mTrashClickListener);//设置Trash的打开及关闭的监听
    }
}

/** Opens/closes the trash in response to clicks on the trash icon. */
protected View.OnClickListener mTrashClickListener = new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // Toggle opened state.
        if (mTrashUi.isOpen()) {
            //点击Trash图标关闭Trash垃圾桶删除block的显示
            closeTrash();
        } else {
            //点击Trash图标显示Trash垃圾桶删除block
            mTrashUi.setCurrentCategory(mTrashCategory);
            closeToolbox();
        }
    }
};

d.而本篇博客要分析的Trash垃圾桶Block的数据的来源最终来自Workspace,存储在Trash垃圾桶Block的

数据保存在对象BlocklyCategory里的mItem字段中：

/**
 * Add a root block to the trash.
 *
 * @param block The block to put in the trash, possibly with descendants attached.
 */
// TODO(#56): Make sure the block doesn't have a parent.
public void addBlockToTrash(Block block) {
    BlocklyCategory.BlockItem blockItem = new BlocklyCategory.BlockItem(block);
    blockItem.getBlock().setEventWorkspaceId(BlocklyEvent.WORKSPACE_ID_TRASH);
    mTrashCategory.addItem(0, blockItem);//在Trash中被删除掉block保存在TrashCategory的mItem字段中
}

三.结合（一）和（二）的分析，现在实现一个原生Blockly中没有实现的功能：在Wrokspace中删除block到Trash中没有对Trash里面的

数据进行Xml的序列化的存储：

1.在原生Blockly中SimpleActivity设置保存Trash垃圾桶block的路径：

private static final String AUTOSAVE_TRASH_FILENAME = "simple_trash_temp.xml";
重写onAutoload()的方法传入保存Workspace和Trash数据的路径： 

@NonNull
@Override
protected String getTrashAutosavePath() {
    return AUTOSAVE_TRASH_FILENAME;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    onAutoload();
}

@Override
protected boolean onAutoload() {
    boolean safely = mBlocklyActivityHelper.loadWorkspaceFromAppDirSafely(AUTOSAVE_FILENAME);
    try {
        mBlocklyActivityHelper.loadTrashFromSdcard(AUTOSAVE_TRASH_FILENAME);
    } catch (IOException e) {
        e.printStackTrace();
    } catch (BlockLoadingException e) {
        e.printStackTrace();
    }
    return safely;
}
 2.在BlcoklyActivityHelper依葫芦画瓢的加入加载和保存的方法：

加载的代码：

/**
 * Loads the workspace from the given file in the application's private data directory.
 * @param filename The path to the file, in the application's local storage.
 * @throws IOException If there is a underlying problem with the input.
 * @throws BlockLoadingException If there is a error with the workspace XML format or blocks.
 */
public void loadWorkspaceFromAppDir(String filename) throws IOException, BlockLoadingException {
    Log.i("yao1" ,"取出loadWorkspaceFromAppDir："+filename);
    mController.loadWorkspaceContents(mActivity.openFileInput(filename));      //把路径传到BlocklyController
}

public void loadTrashFromSdcard(String filename) throws IOException,BlockLoadingException {
    Log.i("yao1" ,"取出loadTrashFromSdcard："+filename);
    mController.loadTrashContents(mActivity.openFileInput(filename));

保存的代码：

/**
 * Save the workspace to the given file in the application's private data directory, and show a
 * status toast. If the save fails, the error is logged.
 */
public void saveWorkspaceToAppDir(String filename)
        throws FileNotFoundException, BlocklySerializerException{
    Workspace workspace = mWorkspaceFragment.getWorkspace();
    workspace.serializeToXml(mActivity.openFileOutput(filename, Context.MODE_PRIVATE)); //将Workspace的数据序列化到xml文件保存
}

public void saveTrashToSdCard(String filename) throws BlocklySerializerException,FileNotFoundException{
    Workspace workspace = mWorkspaceFragment.getWorkspace();
    workspace.serializeTrashToXml(mActivity.openFileOutput(filename, Context.MODE_PRIVATE));
}

3.在Workspace中对Trash里面的block的数据进行xml的保存及读取xml数据转成mTrashCategory：

将mTrashCategory的数据写入xml：

/**
 * Outputs the workspace as an XML string.
 *
 * @param os The output stream to write to.
 * @throws BlocklySerializerException if there was a failure while serializing.
 */
public void serializeToXml(OutputStream os) throws BlocklySerializerException {
    BlocklyXmlHelper.writeToXml(mRootBlocks, os, IOOptions.WRITE_ALL_DATA); //在拖Workspace的mRootBlocks的block写到xml文件中，mRootBlocks即是连接到画布中的block块的集合
}

/**
 * 序列化xml保存数据
 * @param os
 * @throws BlocklySerializerException
 */
public void serializeTrashToXml(OutputStream os) throws BlocklySerializerException {
    //mTrashCategory的字段mItem保存着Trash中的被用户删掉的block,在Workspace中存入mTrashCategory的字段mItem的数据即可
    if (mTrashCategory != null && mTrashCategory.getItems().size() > 0){
        mTrashBlocks.clear();
        for (int i = 0; i < mTrashCategory.getItems().size(); i++) {
            if (BlocklyCategory.BlockItem.TYPE_BLOCK == mTrashCategory.getItems().get(i).getType()) {
                BlocklyCategory.BlockItem blockItem = (BlocklyCategory.BlockItem) mTrashCategory.getItems().get(i);
                mTrashBlocks.add(blockItem.getBlock());
            }
        }
        BlocklyXmlHelper.writeToXml(mTrashBlocks, os, IOOptions.WRITE_ALL_DATA);
    }
}

将xml保存的数据转成mTrashCategory：

/**
 * Reads the workspace in from a XML stream. This will clear the workspace and replace it with
 * the contents of the xml.
 *
 * @param is The input stream to read from.
 * @throws BlockLoadingException If workspace was not loaded. May wrap an IOException or another
 *                               BlockLoadingException.
 */
public void loadWorkspaceContents(InputStream is) throws BlockLoadingException {
    List<Block> newBlocks = BlocklyXmlHelper.loadFromXml(is, mBlockFactory);    //读取自动保存数据转成block的集合

    // Successfully deserialized.  Update workspace.
    // TODO: (#22) Add proper variable support.
    // For now just save and restore the list of variables.
    Set<String> vars = mVariableNameManager.getUsedNames();
    mController.resetWorkspace();
    for (String varName : vars) {
        mController.addVariable(varName);
    }

    mRootBlocks.addAll(newBlocks);  //将加载的block的集合加载到mRootBlocks
    mStats.collectStats(newBlocks, true /* recursive */);
}

public void loadTrashContentsToTrashCategory(InputStream is) throws BlockLoadingException {
    List<Block> newBlocks = BlocklyXmlHelper.loadFromXml(is, mBlockFactory);
    for (int i = 0; i < newBlocks.size(); i++) {
        BlocklyCategory.BlockItem blockItem = new BlocklyCategory.BlockItem(newBlocks.get(i));
        mTrashCategory.addItem(blockItem);
    }
}

以上就实现了Trash垃圾桶被用户删除block的保存与取出，如图所示：

Android关于Blockly对Workspace中的block数据保存及读取的流程，及改造原生代码实现Trash垃圾桶中的block保存及读取


修改Blockly源码实现上述功能的代码地址：http://download.****.net/download/wangyongyao1989/10234076


















 











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