Android_CntextMenu_example_textSize

menu.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <item 
        android:id="@+id/textSize_big"
        android:title="放大"/>
    <item 
        android:id="@+id/textSize_small"
        android:title="缩小"/>

</menu>

layout.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world"
        android:textSize="20sp" />

</RelativeLayout>

main.java

package com.example.day10_contextview;

import android.os.Bundle;
import android.app.Activity;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ContextMenu.ContextMenuInfo;
import android.widget.TextView;
import android.widget.Toast;

/* contextmenu  作用在view
    1.在menu文件的main.xml中编写菜单
    2.在activity中创建菜单
        在onCreateContextMenu方法中创建
        //加载菜单布局
        getMenuInflater().inflate(R.menu.main, menu);
     3.和view进行绑定
          将contextmenu注册到控件
        registerForContextMenu(tvHello);
    4.触发
            长按控件会触发菜单,以对话框的形式展示,点击后自动隐藏
    
    contextmenu和optionsmenu的点击事件都会先触发onMenuItemSelected该方法,
    然后该方法再根据menu特征分发到不同的 菜单相应事件,
    contextmenu触发onContextItemSelected,
    optionsmenu触发onOptionsItemSelected

contextmenu对比optionmenu  
       1.触发条件不一样,optionmenu 点击menu,contextmenu需要长按对应的控件
       2.展示,optionmenu 一级菜单在底部展示,二级以对话框展示,contextmenu直接一对话框展示
       3.作用点 optionmenu是相对于activity的菜单, contextmenu相对于view 
*/
public class MainActivity extends Activity {
    private float size ;
    private TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.text);
        //将contextMenu注册到控件上
        registerForContextMenu(textView);
        
    }
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v,
            ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        //加载菜单布局
        getMenuInflater().inflate(R.menu.main, menu);
        
    }
    /**
     * ContextMenu的点击事件
     * 实现字体的放大缩小功能
     */
    @Override
    public boolean onContextItemSelected(MenuItem item) {
        size = textView.getTextSize();
        switch (item.getItemId()) {
        case R.id.textSize_big:
            size += 5;
            if(size<50){
            textView.setTextSize(size);
            Toast.makeText(MainActivity.this, "TextView的字体大小:"+size+"sp", 0).show();
            }
            break;
        case R.id.textSize_small:
            size -= 5;
            if(size>10){
            textView.setTextSize(size);
            Toast.makeText(MainActivity.this, "TextView的字体大小:"+size+"sp", 0).show();
            break;
        }
        }
        return super.onContextItemSelected(item);
    }

}