Question

我有一个片段，只有一个Button。我的目标是在用户点击该按钮时显示menu_language.xml。我试图在网上找到一个答案，这是我能找到的最接近的答案......但它不起作用：如果我按下按钮没有任何反应。这段代码有什么问题？

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View fgm = inflater.inflate(R.layout.fragment_settings, container, false);
        Button changeLanguageBtn = (Button) fgm.findViewById(R.id.change_language_button);
        changeLanguageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getActivity().openOptionsMenu();
            }
        });
        return fgm;
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View view, ContextMenu.ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, view, menuInfo);
        if (view.getId() == R.id.change_language_button) { // is this even necessary?
            MenuInflater inflater = getActivity().getMenuInflater();
            inflater.inflate(R.menu.menu_language, menu);
        }
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_english:
                // switch to English 
                return true;
            case R.id.action_italian:
                // switch to Italian 
                return true;
            case R.id.action_french:
                // switch to French 
                return true;
            default:
                return super.onContextItemSelected(item);
        }
    }

这里是菜单的xml：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <group android:checkableBehavior="single">
        <item
            android:id="@+id/action_italian"
            android:title="@string/italian" />
        <item
            android:id="@+id/action_english"
            android:title="@string/english" />
        <item
            android:id="@+id/action_french"
            android:title="@string/french" />
    </group>
</menu>

Answer 1

您需要实现选项菜单，您实现了上下文菜单。

see instructions here

Answer 2

我认为你有错误的方法（如果你想在pickStartTime = (TimePicker)findViewById(R.id.timePicker1); pickStartTime.setOnTimeChangedListener(new TimePicker.OnTimeChangedListener() { public void onTimeChanged(TimePicker view, int hourOfDay, int minute) { Log.d("Time", "You picked " + String.valueOf(view.getCurrentHour()) + ":" + String.valueOf(view.getCurrentMinute())); } });添加一个菜单：

ActionBar

如果您阅读该方法＆＃39; Javadoc：

public void onCreateContextMenu(ContextMenu menu, View view, ContextMenu.ContextMenuInfo menuInfo)

鉴于：

/** * Called when a context menu for the {@code view} is about to be shown. * Unlike {@link #onCreateOptionsMenu}, this will be called every * time the context menu is about to be shown and should be populated for * the view (or item inside the view for {@link AdapterView} subclasses, * this can be found in the {@code menuInfo})). * <p> * Use {@link #onContextItemSelected(android.view.MenuItem)} to know when an * item has been selected. * <p> * The default implementation calls up to * {@link Activity#onCreateContextMenu Activity.onCreateContextMenu}, though * you can not call this implementation if you don't want that behavior. * <p> * It is not safe to hold onto the context menu after this method returns. * {@inheritDoc} */

说：

public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {

因此，如果要向活动添加菜单，则必须使用后者。现在，如果您想显示一个锚定在您按下的按钮的上下文菜单，请查看Parsing values from a JSON file using Python?类。

关于您的/** * Initialize the contents of the Activity's standard options menu. You * should place your menu items in to <var>menu</var>. For this method * to be called, you must have first called {@link #setHasOptionsMenu}. See * {@link Activity#onCreateOptionsMenu(Menu) Activity.onCreateOptionsMenu} * for more information. * * @param menu The options menu in which you place your items. * * @see #setHasOptionsMenu * @see #onPrepareOptionsMenu * @see #onOptionsItemSelected */评论，答案是很可能不是。

单击按钮后显示菜单：为什么我的代码不起作用？

2 个答案: