Question

我在ActionMode.Callback内为自定义文字选择功能实施了WebView。我遇到的问题是选择和操作模式状态不匹配。

当我长按时，一切都很好。

Upon long-press, selection highlight appears along with the contextual action bar.

当我与其中一个按钮或WebView（不包括实际选择）进行交互时，ActionMode应该被销毁，选择应该消失。

Selecting a button, or touching outside the selection area. The CAB should close, and the selection should disappear.

在Android 4.4，KitKat中，这正是发生的事情。

然而，这不是4.1.1 - 4.3，Jelly Bean中发生的事情。当我单击其中一个按钮时，不会删除选择。

Tap a button from the contextual action bar. After tapping a button, the selection remains.

当我在选择之外点击时，恰好相反。选择将被删除，但上下文操作栏仍保留在屏幕上。

Tapping the <code>WebView</code> after the selection starts. The selection is cleared, but the contextual action bar remains.

<小时/> 以下是我的CustomWebView

的代码

public class CustomWebView extends WebView {

    private ActionMode.Callback mActionModeCallback;

    @Override
    public ActionMode startActionMode(Callback callback) {
        ViewParent parent = getParent();
        if (parent == null) {
            return null;
        }
        mActionModeCallback = new CustomActionModeCallback();
        return parent.startActionModeForChild(this, mActionModeCallback);
    }

    private class CustomActionModeCallback implements ActionMode.Callback {

        // Called when the action mode is created; startActionMode() was called
        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            // Inflate a menu resource providing context menu items
            MenuInflater inflater = mode.getMenuInflater();
            inflater.inflate(R.menu.contextual_menu, menu);
            return true;
        }

        // Called each time the action mode is shown.
        // Always called after onCreateActionMode, but
        // may be called multiple times if the mode is invalidated.
        @Override
        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
            // This method is called when the handlebars are moved.
            loadJavascript("javascript:getSelectedTextInfo()");
            return false; // Return false if nothing is done
        }

        // Called when the user selects a contextual menu item
        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            switch(item.getItemId() {
            case R.id.button_1:
                // do stuff
                break;
            ...
            default:
                break;
            }

            mode.finish(); // Action picked, so close the CAB
            return true;
        }

        // Called when the user exits the action mode
        @Override
        public void onDestroyActionMode(ActionMode mode) {
            // TODO This does not work in Jelly Bean (API 16 - 18; 4.1.1 - 4.3).
            clearFocus(); // Remove the selection highlight and handles.

        }
    }
}

正如上面的评论所示，我认为问题出在clearFocus()方法上。当我删除该方法时，按下一个按钮会使选择落后于4.4，就像Jelly Bean中的行为一样。 clearFocus()给出了4.4中的预期行为，但未转移到早期的API。（请注意，clearFocus()对于KitKat来说并不陌生;它自API 1以来一直在Android中。）

如何解决这个问题？

Answer 1

经过多次尝试解决这个问题，我终于明白了！

重要的是要知道Android 4.4（KitKat）之前的WebView与典型的浏览器不同。有一些隐藏的类可以开始搞乱事情。有WebViewCore可以完成所有繁重的工作并实际产生结果，并且WebViewClassic是这个问题的罪魁祸首。

解决方案是半黑客攻击，因为你不需要做任何操作来操作底层类，但你必须抓住问题场景。

WebViewClassic负责拦截长按并处理它们以进行文本选择，包括选择突出显示和选择控制柄的动画，以及启动填充上下文操作栏的ActionMode（出租车）。不幸的是，由于我们希望用我们自己的方式覆盖ActionMode，因此文本选择和CAB变得不同步，因为它们彼此不相关。要解决此问题，请跟踪您自己的自定义ActionMode.Callback，以及与选择动画相关联的ActionMode.Callback。然后，当您的ActionMode.Callback被销毁时，请调用选择的finish()方法以销毁该ActionMode.Callback。

好的，说得够多;这是代码。

public class CustomWebView extends WebView {

    private ActionMode mActionMode;
    private ActionMode.Callback mActionModeCallback;
    // Add this class variable
    private ActionMode.Callback mSelectActionModeCallback;

    @Override
    public ActionMode startActionMode(Callback callback) {
        /* When running Ice Cream Sandwich (4.0) or Jelly Bean (4.1 - 4.3), there
         * is a hidden class called 'WebViewClassic' that draws the selection.
         * In order to clear the selection, save the callback from Classic
         * so it can be destroyed later.
         */
        // Check the class name because WebViewClassic.SelectActionModeCallback
        // is not public API.
        String name = callback.getClass().toString();
        if (name.contains("SelectActionModeCallback")) {
            mSelectActionModeCallback = callback;
        }
        mActionModeCallback = new CustomActionModeCallback();
        // We haven't actually done anything yet. Send our custom callback 
        // to the superclass so it will be shown on screen.
        return super.startActionModeForChild(this, mActionModeCallback);
    }

    private class CustomActionModeCallback implements ActionMode.Callback {

        // Called when the action mode is created; startActionMode() was called
        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            // This is important for part 2.
            mActionMode = mode;
            // Inflate a menu resource providing context menu items
            MenuInflater inflater = mode.getMenuInflater();
            inflater.inflate(R.menu.contextual_menu, menu);
            return true;
        }

        // Called each time the action mode is shown.
        // Always called after onCreateActionMode, but
        // may be called multiple times if the mode is invalidated.
        @Override
        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
            // This method is called when the handlebars are moved.
            loadJavascript("javascript:getSelectedTextInfo()");
            return false; // Return false if nothing is done
        }

        // Called when the user selects a contextual menu item
        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            switch(item.getItemId() {
            case R.id.button_1:
                // do stuff
                break;
            ...
            default:
                break;
            }

            mode.finish(); // Action picked, so close the CAB
            return true;
        }

        // Called when the user exits the action mode
        @Override
        public void onDestroyActionMode(ActionMode mode) {
            clearFocus(); // Remove the selection highlight and handles.

            // Semi-hack in order to clear the selection
            // when running Android earlier than KitKat.
            if (mSelectActionModeCallback != null) {
                mSelectActionModeCallback.onDestroyActionMode(mode);
            }
            // Relevant to part 2.
            mActionMode = null;
        }
    }
}

<小时/> 信不信由你，我们只完成了一半。上面的代码负责在CAB关闭时删除选择。要在触摸事件中关闭CAB，我们必须做更多的工作。这一次，它更加直截了当。我使用GestureDetector并收听单击事件。当我收到该活动时，我会在finish()上致电mActionMode关闭CAB：

public class CustomWebView extends WebView {

    private ActionMode mActionMode; 
    private ActionMode.Callback mActionModeCallback;
    private ActionMode.Callback mSelectActionModeCallback;

    // Code from above segment
    ...

    private class CustomGestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onSingleTapUp(MotionEvent e) {
            if (mActionMode != null) {
                mActionMode.finish();
                return true;
            }
            return false;
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // Send the event to our gesture detector
        // If it is implemented, there will be a return value
        this.mDetector.onTouchEvent(event);
        // If the detected gesture is unimplemented, send it to the superclass
        return super.onTouchEvent(event);
    }

}

<小时/> 这应该做到！我们做到了！

在其他任何地方都找不到WebViewClassic素材;这就是为什么我提供了很多关于发生了什么的细节。调试器花了很多时间来弄清楚发生了什么。幸运的是，GestureDetector类已有详细记录，并包含多个教程。我从Android Developers website获取了我的信息。我希望这能帮助那些像我一样努力解决这个问题的人。：）

Webview文本选择不清除

1 个答案: