Android按键之Menu介绍
Android手机一般都有三个键,返回键、Home键、菜单键;
Android系统的菜单支持主要通过4个接口来实现。
从上图可以看出Menu是一个父类接口,它下面有两个子类一个是ContextMenu:它表示是一个上下文菜单,SubMenu表示一个子菜单。它们都可以包含一个或多个的MenuItem菜单项
Menu接口定义了两个方法来添加菜单项和添加子菜单。一个通过add()方法添加菜单项,addSubMenu()方法来添加子菜单。而SubMenu与ContextMenu继承了Munu接口的方法之外,还提供了一些的方法。比如设置菜单的标题、图标等;
开发菜单和子菜单有两种方式;一是在Activity重写的方法onCreateOptionsMenu(Menu menu)方法中调用menu对象添加,然后在重写Activity的onOptionsItemSelected来响应选择的菜单项。二是通过资源文件来定义菜单项,然后在onCreateOptionsMenu方法中加载这个xml资源。onCreateOptionsMenu方法在单击Menu键时触发。
而开发上下文菜单与上类似:分为三个步骤:一是重写onCreateContextMenu(ContextMenu menu,View source,ContextMenu.MenuInfo info)方法,然后调用registerForContextMenu(View viwe)方法为控件注册上下文菜单,最后重写onContextItemSelected(Menuitem item)来响应选择的菜单项
实例如下:
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1、代码中添加:
package com.android.xiong.memu; import android.os.Bundle; import android.app.Activity; import android.app.AlertDialog; import android.app.AlertDialog.Builder; import android.view.ContextMenu; import android.view.ContextMenu.ContextMenuInfo; import android.view.Menu; import android.view.MenuItem; import android.view.SubMenu; import android.view.View; import android.widget.Button; public class MainActivity extends Activity { // 定义菜单项的ItemId private final int NEWS = 00; private final int COLOR = 01; private final int FONT = 02; private final int RED = 001; private final int BULE = 002; private final int GREED = 003; private final int BIG = 004; private final int SMALL = 005; Builder bu; Button show; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); bu = new AlertDialog.Builder(this); show = (Button) findViewById(R.id.context); // 为Button注册上下文菜单 registerForContextMenu(show); } // 用户单击Menu键时触发 @Override public boolean onCreateOptionsMenu(Menu menu) { // 添加新建菜单项 menu.add(0, NEWS, 0, "新建"); // 添加颜色子菜单 SubMenu color = menu.addSubMenu(0, COLOR, 0, "颜色"); color.setHeaderTitle("选择颜色"); color.add(0, RED, 0, "红色"); color.add(0, BULE, 0, "蓝色"); color.add(0, GREED, 0, "绿色"); // 添加字体的菜单 SubMenu font = menu.addSubMenu(0, FONT, 0, "字体"); font.setHeaderTitle("选择字体"); font.add(0, BIG, 0, "大字体"); font.add(0, SMALL, 0, "小字体"); return super.onCreateOptionsMenu(menu); } // 当用户单击菜单项触发 @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case RED: bu.setMessage("红色").setPositiveButton("确定", null).show(); break; case BULE: bu.setMessage("蓝色").setPositiveButton("确定", null).show(); break; case GREED: bu.setMessage("绿色").setPositiveButton("确定", null).show(); break; case BIG: bu.setMessage("大号").setPositiveButton("确定", null).show(); break; case SMALL: bu.setMessage("小号").setPositiveButton("确定", null).show(); break; case NEWS: bu.setMessage("新建").setPositiveButton("确定", null).show(); break; } return true; } // 长按组件响应的上下文菜单 @Override public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { menu.add(0, RED, 0, "红色"); menu.add(0, BULE, 0, "蓝色"); menu.add(0, GREED, 0, "绿色"); } // 点击上下文菜单项触发 @Override public boolean onContextItemSelected(MenuItem item) { switch (item.getItemId()) { case RED: bu.setMessage("红色").setPositiveButton("确定", null).show(); break; case BULE: bu.setMessage("蓝色").setPositiveButton("确定", null).show(); break; case GREED: bu.setMessage("绿色").setPositiveButton("确定", null).show(); break; } return true; } }
2、XML资源定义菜单
<menu xmlns:android="http://schemas.android.com/apk/res/android" > <!-- 添加菜单项 --> <item android:id="@+id/menu_news" android:title="@string/news"/> <!-- 添加子菜单 --> <item android:title="@string/color" > <menu> <!-- 单项选择 --> <group android:checkableBehavior="single"> <!-- 选中红色 --> <item android:id="@+id/color_red" android:checked="true" android:title="@string/red"/> <item android:id="@+id/color_bule" android:title="@string/bule"/> <item android:id="@+id/color_greed" android:title="@string/greed"/> </group> </menu> </item> <item android:title="@string/font" > <menu> <!-- 多项选择 --> <group android:checkableBehavior="all"> <item android:id="@+id/font_big" android:title="@string/big"/> <item android:id="@+id/font_Small" android:title="@string/small"/> </group> </menu> </item> </menu>
package com.android.xiong.menu2; import android.os.Bundle; import android.app.Activity; import android.app.AlertDialog; import android.app.AlertDialog.Builder; import android.view.ContextMenu; import android.view.ContextMenu.ContextMenuInfo; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.widget.Button; public class MainActivity extends Activity { Button show; Builder bu; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); bu = new AlertDialog.Builder(this); show=(Button)findViewById(R.id.bt_show); registerForContextMenu(show); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.main, menu); return super.onCreateOptionsMenu(menu); } @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.color_red: bu.setMessage("红色").setPositiveButton("确定", null).show(); break; case R.id.color_bule: bu.setMessage("蓝色").setPositiveButton("确定", null).show(); break; case R.id.color_greed: bu.setMessage("绿色").setPositiveButton("确定", null).show(); break; case R.id.font_big: bu.setMessage("大号").setPositiveButton("确定", null).show(); break; case R.id.font_Small: bu.setMessage("小号").setPositiveButton("确定", null).show(); break; case R.id.menu_news: bu.setMessage("新建").setPositiveButton("确定", null).show(); break; } return true; } @Override public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { getMenuInflater().inflate(R.menu.main, menu); } @Override public boolean onContextItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.color_red: bu.setMessage("红色").setPositiveButton("确定", null).show(); break; case R.id.color_bule: bu.setMessage("蓝色").setPositiveButton("确定", null).show(); break; case R.id.color_greed: bu.setMessage("绿色").setPositiveButton("确定", null).show(); break; case R.id.font_big: bu.setMessage("大号").setPositiveButton("确定", null).show(); break; case R.id.font_Small: bu.setMessage("小号").setPositiveButton("确定", null).show(); break; case R.id.menu_news: bu.setMessage("新建").setPositiveButton("确定", null).show(); break; } return true; } }
PopMenu表示一个弹出式菜单:使用的的步骤1、创建PopupMenu对象;2、通过MenuInflater的inflate()方法将菜单填充到PopupMenu中3、调用PopupMenu的show()方法显示弹出菜单
实例:
<menu xmlns:android="http://schemas.android.com/apk/res/android" > <group android:checkableBehavior="single"> <item android:id="@+id/red" android:title="@string/red"/> <item android:id="@+id/bule" android:title="@string/bule"/> <item android:id="@+id/greed" android:title="@string/greed"/> </group> </menu>
package com.android.xiong.home; import android.annotation.SuppressLint; import android.app.Activity; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.PopupMenu; import android.widget.PopupMenu.OnMenuItemClickListener; import android.widget.Toast; @SuppressLint("NewApi") public class MainActivity extends Activity { Button show; PopupMenu pop; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); show=(Button)findViewById(R.id.show); setPopupMenu(show); show.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { pop.show(); } }); } public void setPopupMenu(View v){ //创建PopupMenu对象 pop=new PopupMenu(this, v); //将菜单资源加载到Pop中 getMenuInflater().inflate(R.menu.main,pop.getMenu()); pop.setOnMenuItemClickListener(new OnMenuItemClickListener() { @Override public boolean onMenuItemClick(MenuItem item) { switch (item.getItemId()) { case R.id.red: Toast.makeText(MainActivity.this, "红色", Toast.LENGTH_SHORT).show(); break; case R.id.bule: Toast.makeText(MainActivity.this, "蓝色", Toast.LENGTH_SHORT).show(); break; case R.id.greed: Toast.makeText(MainActivity.this, "绿色", Toast.LENGTH_SHORT).show(); break; } return false; } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }
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