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/*这段代码展示了如何在 Android 应用程序中实现一个带有弹出菜单的下拉按钮。
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这个 DropdownMenu 类封装了创建一个带有菜单的按钮所需的所有步骤。 */
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/*
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* Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package net.micode.notes.ui;
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import android.content.Context;
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import android.view.Menu;
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import android.view.MenuItem;
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import android.view.View;
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import android.view.View.OnClickListener;
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import android.widget.Button;
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import android.widget.PopupMenu;
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import android.widget.PopupMenu.OnMenuItemClickListener;
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import net.micode.notes.R;
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public class DropdownMenu { /*定义了一个名为 DropdownMenu 的公共类*/
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private Button mButton;
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private PopupMenu mPopupMenu;
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private Menu mMenu; /*声明了一些私有变量，分别代表按钮、弹出菜单和菜单对象。*/
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public DropdownMenu(Context context, Button button, int menuId) {
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mButton = button;
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mButton.setBackgroundResource(R.drawable.dropdown_icon); /*构造函数初始化成员变量，设置按钮的背景图片*/
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mPopupMenu = new PopupMenu(context, mButton);
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mMenu = mPopupMenu.getMenu();
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mPopupMenu.getMenuInflater().inflate(menuId, mMenu);/*创建 PopupMenu 实例，获取菜单对象，并通过提供的菜单资源 ID 充气菜单*/
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mButton.setOnClickListener(new OnClickListener() {
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public void onClick(View v) {
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mPopupMenu.show();
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}
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});
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} /*为按钮设置点击监听器，点击时显示弹出菜单*/
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public void setOnDropdownMenuItemClickListener(OnMenuItemClickListener listener) {
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if (mPopupMenu != null) {
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mPopupMenu.setOnMenuItemClickListener(listener);
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}
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} /*设置弹出菜单项点击监听器的方法，允许外部设置监听器以便处理菜单项点击事件*/
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public MenuItem findItem(int id) {
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return mMenu.findItem(id);
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} /*提供一个方法用于根据资源 ID 查找菜单项*/
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public void setTitle(CharSequence title) {
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mButton.setText(title);
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}/*设置按钮文本的方法*/
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}
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/*这个 DropdownMenu 类使得在应用程序中添加带有弹出菜单的按钮变得更加容易，通过构造函数传入上下文、按钮和菜单资源 ID，就可以轻松地创建和使用带有菜单的按钮。*/
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