tab手势跳转activity

在网上找了好久，终于找到一个简单易懂，比较合适的例子，有那么2行代码我也看不太懂，看不懂的可以留言，咱们一起探讨，代码如下

 package com.mars.mp3player;

 import android.app.TabActivity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.GestureDetector;
 import android.view.GestureDetector.SimpleOnGestureListener;
 import android.view.Menu;
 import android.view.MotionEvent;
 import android.view.View;
 import android.widget.TabHost;
 import android.widget.TabHost.TabSpec;

 public class ActivityMain extends TabActivity {
     private TabSpec tabSpec;
     private TabHost tabHost;
     private Intent intent;
     // *********************************
     private static final int SWIPE_MIN_DISTANCE = 120;
     private static final int SWIPE_MAX_OFF_PATH = 250;
     private static final int SWIPE_THRESHOLD_VELOCITY = 200;
     private GestureDetector gestureDetector;
     View.OnTouchListener gestureListener;

     int currentView = 0;
     private static int maxTabIndex = 2;

     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         super.setContentView(R.layout.activity_main);
         UtilVar.activities.add(ActivityMain.this);
         this.initTableHost();

         gestureDetector = new GestureDetector(new MyGestureDetector());
         gestureListener = new View.OnTouchListener() {
             public boolean onTouch(View v, MotionEvent event) {
                 if (gestureDetector.onTouchEvent(event)) {
                     return true;
                 }
                 return false;
             }
         };

     }

     /**
      * tablehost的初始化，代码完成
      */
     private void initTableHost() {
         tabHost = super.getTabHost();
         // 歌曲列表
         intent = new Intent(ActivityMain.this, ActivityList.class);
         tabSpec = tabHost
                 .newTabSpec("歌曲列表")
                 .setIndicator("歌曲列表",
                         getResources().getDrawable(R.drawable.ic_launcher))
                 .setContent(intent);
         tabHost.addTab(tabSpec);
         // 正在播放
         intent = new Intent(ActivityMain.this, ActivityPlaying.class);
         tabSpec = tabHost
                 .newTabSpec("正在播放")
                 .setIndicator("正在播放",
                         getResources().getDrawable(R.drawable.ic_launcher))
                 .setContent(intent);
         tabHost.addTab(tabSpec);
         // 专辑列表
         intent = new Intent(ActivityMain.this, ActivityLyric.class);
         tabSpec = tabHost
                 .newTabSpec("歌词显示")
                 .setIndicator("歌词显示",
                         getResources().getDrawable(R.drawable.ic_launcher))
                 .setContent(intent);
         tabHost.addTab(tabSpec);
         // 设置当前tab
         tabHost.setCurrentTab(1);
     }

     // 左右滑动刚好页面也有滑动效果
     class MyGestureDetector extends SimpleOnGestureListener {
         @Override
         public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                 float velocityY) {
             TabHost tabHost = getTabHost();
             System.out.println("************");
             try {
                 if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                     return false;
                 // right to left swipe
                 if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
                         && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                     Log.i("test", "right");
                     if (currentView == maxTabIndex) {
                         currentView = 0;
                     } else {
                         currentView++;
                     }
                     tabHost.setCurrentTab(currentView);
                 } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
                         && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                     Log.i("test", "left");
                     if (currentView == 0) {
                         currentView = maxTabIndex;
                     } else {
                         currentView--;
                     }
                     tabHost.setCurrentTab(currentView);
                 }
             } catch (Exception e) {
             }
             return false;
         }
     }

     @Override
     public boolean dispatchTouchEvent(MotionEvent event) {
         if (gestureDetector.onTouchEvent(event)) {
             event.setAction(MotionEvent.ACTION_CANCEL);
         }
         return super.dispatchTouchEvent(event);
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.activity_main, menu);
         return true;
     }

 }
 // 主要代码就这样吧，以后就不必到处找手势跳转activity的例子了。