Android事件处理机制，Toast控件

package com.lxt008;

import com.lxt008.R;

import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
/**
 * 
 * 控件事件通过设置其控件的监听器来监听并处理事件
 * 按键按下事件：通过重写onKeyDown方法
 * 按键弹起事件：通过重写onKeyUp方法
 * 触笔点击事件：通过实现onTouchEvent方法
 * 示例中使用了Toast控件：
 * Toast.makeText(this, string, Toast.LENGTH_SHORT).show();
 * 显示提示信息
 *
 */

public class Activity01 extends Activity
{

    public void onCreate(Bundle savedInstanceState)
    {

        super.onCreate(savedInstanceState);
        
        setContentView(R.layout.main);
        //获得Button对象
        Button button_ok = (Button) findViewById(R.id.ok);
        //设置Button控件监听器
        button_ok.setOnClickListener(new Button.OnClickListener() {
            public void onClick(View v)
            {
                //这里处理事件
                DisplayToast("点击了OK按钮");
            }
        });

    }

    /* 按键按下所触发的事件 */
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        switch (keyCode)
        {
            case KeyEvent.KEYCODE_DPAD_CENTER:
                DisplayToast("按下：中键");
                break;
            case KeyEvent.KEYCODE_DPAD_UP:
                DisplayToast("按下：上方向键");
                break;
            case KeyEvent.KEYCODE_DPAD_DOWN:
                DisplayToast("按下：下方向键");
                break;
            case KeyEvent.KEYCODE_DPAD_LEFT:
                DisplayToast("按下：左方向键");
                break;
            case KeyEvent.KEYCODE_DPAD_RIGHT:
                DisplayToast("按下：右方向键");
                break;
        }
        return super.onKeyDown(keyCode, event);
    }
    /* 按键弹起所触发的事件 */
    public boolean onKeyUp(int keyCode, KeyEvent event)
    {
        switch (keyCode)
        {
            case KeyEvent.KEYCODE_DPAD_CENTER:
                DisplayToast("弹起：中键");
                break;
            case KeyEvent.KEYCODE_DPAD_UP:
                DisplayToast("弹起：上方向键");
                break;
            case KeyEvent.KEYCODE_DPAD_DOWN:
                DisplayToast("弹起：下方向键");
                break;
            case KeyEvent.KEYCODE_DPAD_LEFT:
                DisplayToast("弹起：左方向键");
                break;
            case KeyEvent.KEYCODE_DPAD_RIGHT:
                DisplayToast("弹起：右方向键");
                break;
        }
        
        return super.onKeyUp(keyCode, event);
    }
    
    public boolean onKeyMultiple(int keyCode, int repeatCount, KeyEvent event)
    {
        
        return super.onKeyMultiple(keyCode, repeatCount, event);
    }
    
    /* 触笔事件 */
    public boolean onTouchEvent(MotionEvent event)
    {
        int iAction = event.getAction();
        if (iAction == MotionEvent.ACTION_CANCEL || 
            iAction == MotionEvent.ACTION_DOWN || 
            iAction == MotionEvent.ACTION_MOVE) 
        {
            return false;
        }
        //得到触笔点击的位置
        int x = (int) event.getX();
        int y = (int) event.getY();
        
        DisplayToast("触笔点击坐标：("+Integer.toString(x)+","+Integer.toString(y)+")");
        
        return super.onTouchEvent(event);
    }
    
    /* 显示Toast  */
    public void DisplayToast(String str)
    {
        Toast.makeText(this, str, Toast.LENGTH_SHORT).show();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
    <Button
    android:id="@+id/ok"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="OK"/>
</LinearLayout>