图库Gallery3D(Gallery2)分析(四) 菜单命令执行过程分析

时间：2014-07-10 20:06:08 阅读：690 评论：0 收藏：0 [点我收藏+]

该分析基于 Android4.2的Gallery2

1 菜单创建过程分析。

Gallery的父类是AbstractGalleryActivity类，AbstractGalleryActivity的父类是Activity类。所以菜单创建是调用的AbstractGalleryActivity的菜单创建函数。

public class AbstractGalleryActivity extends Activity implements GalleryContext {
    private static final String TAG = "AbstractGalleryActivity";
    private StateManager mStateManager;
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        return getStateManager().createOptionsMenu(menu);
}
}

每一个子页面(比如PhotoPage)都是ActivityState的子类。StateManager是一个子页面(ActivityState)管理类,负责子页面切换，命令执行，界面刷新等职能。Gallery将所有操作命令交给StateManager执行，StateManager再将命令分发给当前子页面执行。

public class StateManager {
    private static final String TAG = "StateManager";
    private AbstractGalleryActivity mActivity;
    private Stack<StateEntry> mStack = new Stack<StateEntry>();
 
    public boolean createOptionsMenu(Menu menu) {
        if (mStack.isEmpty()) {
            return false;
        } else {
            return getTopState().onCreateActionBar(menu);
        }
}
 
public ActivityState getTopState() {
     Utils.assertTrue(!mStack.isEmpty());
     return mStack.peek().activityState;
}
}

StateManager将创建菜单操作，分发给当前子页面(以PhotoPage为例)执行。子页面根据页面属性配置并更新一下MenuExecutor。这样就完成了菜单的创建工作。

public class PhotoPage extends ActivityState{
    private static final String TAG = "PhotoPage";
    @Override
    protected boolean onCreateActionBar(Menu menu) {
        mActionBar.createActionBarMenu(R.menu.photo, menu);
        mHaveImageEditor = GalleryUtils.isEditorAvailable(mActivity, "image/*");
        updateMenuOperations();
        mActionBar.setTitle(mMediaSet != null ? mMediaSet.getName() : "");
        return true;
}
}

2 菜单命令的执行。

Gallery的父类是AbstractGalleryActivity类，AbstractGalleryActivity的父类是Activity类。所以菜单创建是调用的AbstractGalleryActivity的菜单命令执行函数。

public class AbstractGalleryActivity extends Activity implements GalleryContext {
    private static final String TAG = "AbstractGalleryActivity";
    private StateManager mStateManager;
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        GLRoot root = getGLRoot();
        root.lockRenderThread();
        try {
            return getStateManager().itemSelected(item);
        } finally {
            root.unlockRenderThread();
        }
}
}

StateManager再将菜单命令分发给当前显示的子页面(以PhotoPage为例)

public class StateManager {
    private static final String TAG = "StateManager";
    private AbstractGalleryActivity mActivity;
    private Stack<StateEntry> mStack = new Stack<StateEntry>();
 
    public boolean itemSelected(MenuItem item) {
        if (!mStack.isEmpty()) {
            if (getTopState().onItemSelected(item)) return true;
            if (item.getItemId() == android.R.id.home) {
                if (mStack.size() > 1) {
                    getTopState().onBackPressed();
                }
                return true;
            }
        }
        return false;
}
}

当前显示的子页面(以PhotoPage为例)，最终承担命令的执行工作。其中涉及到文件操作，又会分发到MenuExecutor处理。比如删除操作，MenuExecutor内部会生成一个删除任务，然后交给线程池执行该任务，有兴趣可以看下这部分代码，这里就省略掉了。采用任务-线程池的方式优点是：耗时操作，界面不会卡顿；任务可以随时取消，快速多次操作不影响系统流畅度和稳定性。

public class PhotoPage extends ActivityState{
    private static final String TAG = "PhotoPage";
    @Override
protected boolean onItemSelected(MenuItem item) {
　MediaItem current = mModel.getMediaItem(0);
　int currentIndex = mModel.getCurrentIndex();
　Path path = current.getPath();
　DataManager manager = mActivity.getDataManager();
　int action = item.getItemId();
　String confirmMsg = null;
　switch (action) {
   　case R.id.action_edit: {
　　launchPhotoEditor();return true;
　　　}
    　case R.id.action_details: {
     　showDetails();return true;
    　}
    　case R.id.action_delete:
        　confirmMsg = mActivity.getResources().getQuantityString(
             R.plurals.delete_selection, 1);
　　　　　mMenuExecutor.onMenuClicked(item, confirmMsg,
                        new ImportCompleteListener(mActivity));
　　}
｝
}