Android按键之Menu详解
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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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
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：
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;
}
}