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如果AbsListView.setItemChecked()直接调用，效果很好，ActionMode会激活并创建。

mGridView.setItemChecked(pPosition, true);

但是当你View.startActionMode()先调用，然后调用AbsListView.setItemChecked()时，ActionModecreate bystartActionMode()将销毁，并重新创建一个新的 by setItemChecked()。

我的问题是：第一次打电话时如何避免这个问题View.startActionMode()？

期待你的答复！谢谢！

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1 回答 1

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为什么要重新创建一个新的？查看方法的源码AbsListView.setItemChecked(int position, boolean value)，可以看到如下代码：</p> 

    // Start selection mode if needed. We don't need to if we're unchecking something.
    if (value && mChoiceMode == CHOICE_MODE_MULTIPLE_MODAL && mChoiceActionMode == null) {
        if (mMultiChoiceModeCallback == null ||
                !mMultiChoiceModeCallback.hasWrappedCallback()) {
            throw new IllegalStateException("AbsListView: attempted to start selection mode " +
                    "for CHOICE_MODE_MULTIPLE_MODAL but no choice mode callback was " +
                    "supplied. Call setMultiChoiceModeListener to set a callback.");
        }
        mChoiceActionMode = startActionMode(mMultiChoiceModeCallback);
    }

这意味着如果mChoiceActionMode == null，它将调用startActionMode(mMultiChoiceModeCallback)，因此将重新创建一个新的 ActionMode。

以及如何解决？这是一个简单的方法：使用反射将ActionMode create by 分配给.startActionMode()中的私有字段mChoiceActionMode。AbsListView

private void startActionMode() {
    // Get the field "mMultiChoiceModeCallback" instance by reflect
    AbsListView.MultiChoiceModeListener wrapperIns = null;
    try {
        Field wrapper = null;
        wrapper = AbsListView.class.getDeclaredField("mMultiChoiceModeCallback");
        wrapper.setAccessible(true);
        wrapperIns = (AbsListView.MultiChoiceModeListener) wrapper.get(mMessageGridView);
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    }
    // Start the ActionMode, but not select any item. 
    ActionMode actionMode = mMessageGridView.startActionMode(wrapperIns);
    // Assign actionMode to field "mChoiceActionMode" by reflect 
    try {
        Field mChoiceActionMode = null;
        mChoiceActionMode = AbsListView.class.getDeclaredField("mChoiceActionMode");
        mChoiceActionMode.setAccessible(true);
        mChoiceActionMode.set(mMessageGridView, actionMode);
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    }
}

为什么我们在这里使用包装器？因为AbsListView.setMultiChoiceModeListener(MultiChoiceModeListener listener)会包装我们的mMultiChoiceModeListener，所以我们不能不直接使用。

于 2015-03-04T09:41:55.720 回答