ViewPager控件的Demo

<LinearLayout 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:orientation="vertical"
>

<include layout="@layout/head"/>
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:id="@+id/vp"
/>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="10dip"
android:orientation="horizontal" >

<TextView
android:id="@+id/tvChat"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:text="聊天" />

<TextView
android:id="@+id/tvFriend"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:text="朋友" />

<TextView
android:id="@+id/tvContact"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:text="通讯" />
</LinearLayout>
<ImageView
android:id="@+id/iv_scroll"
android:layout_width="100dip"
android:layout_height="wrap_content"
android:background="@drawable/ivbg"
/>
<TextView
android:layout_width="match_parent"
android:layout_height="1dip"
android:background="#000000"
/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="我在聊天"
/>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="我的朋友"
/>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="我的通讯"
/>

</LinearLayout>

package com.zyhui.viewpagerdemo;

import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Display;
import android.view.Menu;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.LinearLayout;

public class MainActivity extends FragmentActivity {
private List<Fragment> fragList;
private ViewPager vp;
private ImageView iv_scroll;
private int screenWidth;
private LinearLayout.LayoutParams lp;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

iv_scroll = (ImageView) findViewById(R.id.iv_scroll);

//获取屏幕宽
screenWidth = getScreenWH()[0];
//设置iv_scroll的宽和高
lp = (LinearLayout.LayoutParams)iv_scroll.getLayoutParams();//为什么要这样呢?
lp.width = screenWidth/3;

initFragment();
initViewPager();

setVpEvent();
}

private void initViewPager() {
vp = (ViewPager) findViewById(R.id.vp);
vp.setAdapter(new MyAdapter(getSupportFragmentManager()));
vp.setCurrentItem(0);
}

private void initFragment() {
fragList = new ArrayList<Fragment>();
fragList.add(new FragmentChat());
fragList.add(new FragmentFriend());
fragList.add(new FragmentContact());
}

private class MyAdapter extends FragmentPagerAdapter{

public MyAdapter(FragmentManager fm) {
super(fm);

}

@Override
public Fragment getItem(int position) {
return fragList.get(position);
}

@Override
public int getCount() {
return fragList.size();
}

}

private void setVpEvent() {
vp.setOnPageChangeListener(new OnPageChangeListener() {
private int currentIndex = 0;//这个初始值应当为0,而不要为-1,否则默认是显示不了iv_scroll的图片的，因为leftMargin的值会为负值
//选中页面时候调用的方法
//index表示当前选中的页
@Override
public void onPageSelected(int index) {
currentIndex = index;
}

//页面滑动时候调用的方法
//position是向右滑动到下一个页面时position==index,向左滑动position-index=1
//offset:向右滑动到下一个页面时，它的值从0.00到0.99;向做滑动时，从0.99到0.00
//offsetPixels:向右滑动到下一个页面时，它从0到屏幕的宽度;向左滑动时是从屏幕宽度到0
@Override
public void onPageScrolled(int position, float offset, int offsetPixels) {
//经测试，感觉不用这个判断也可以，直接使用lp.leftMargin = (screenWidth/3)*currentIndex就行了，这样右移感觉不到卡
if(position == currentIndex){//向右滑动
lp.leftMargin = (int) ((screenWidth/3)*currentIndex + offset * (screenWidth/3));
//lp.leftMargin = (screenWidth/3)*currentIndex;
Log.i("zyh", currentIndex + "========>" + offset+"R");
//Log.i("zyh", "右移");//感觉没有左移的输出
iv_scroll.setLayoutParams(lp);
}else if(position - currentIndex == 1){//向左滑动
lp.leftMargin = (int) ((screenWidth/3) * currentIndex - (1 - offset) * (screenWidth/3));
//lp.leftMargin = (screenWidth/3)*currentIndex;
Log.i("zyh", currentIndex + "========>" + offset+"L");
//Log.i("zyh", "左移");//感觉没有左移的输出
iv_scroll.setLayoutParams(lp);
}

}

//滑动状态改变时调用的方法
//state有3个值:
//0表示什么多不干
//1表示正在滑动
//2表示
@Override
public void onPageScrollStateChanged(int state) {

}
});
}

/**
* @desc 获取屏幕的宽高
* @return
*/
private int[] getScreenWH() {
WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
DisplayMetrics outMetrics = new DisplayMetrics();
display.getMetrics(outMetrics);
return new int[]{outMetrics.widthPixels,outMetrics.heightPixels};
}

}

package com.zyhui.viewpagerdemo;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class FragmentChat extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {

return inflater.inflate(R.layout.frag_chat, null);
}
}