Android学习笔记：使用ViewPager组件实现图片切换

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
   <android.support.v4.view.ViewPager  
        android:id="@+id/viewPager"  
        android:layout_width="match_parent"  
        android:layout_height="wrap_content" /> 
        
    <RelativeLayout  
        android:layout_width="match_parent"  
        android:layout_height="wrap_content" 
        android:orientation="vertical" >  
  
        <LinearLayout  
            android:id="@+id/tagView"  
            android:layout_width="match_parent"  
            android:layout_height="wrap_content"  
            android:layout_alignParentBottom="true" 
            android:layout_marginBottom="20dp"  
            android:gravity="center_horizontal"  
            android:orientation="horizontal" >  
        </LinearLayout>  
    </RelativeLayout>  

</FrameLayout>

package com.example.showviewpager;

import java.util.ArrayList;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;

public class MainActivity extends Activity {

	private static final int VIEW_NUM = 5;
	private ViewPager viewPager;
	private ImageView[] tagImageViews = new ImageView[VIEW_NUM];

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		addTagImage();
		initViewPager();
	}

	private void addTagImage() {
		LinearLayout layout = (LinearLayout)findViewById(R.id.tagView);
		LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
		 LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
		params.setMargins(15, 0, 0, 0);
		for (int i = 0; i < VIEW_NUM; i++) {
			ImageView tagImageView = new ImageView(this);
			tagImageView.setLayoutParams(params);
			tagImageViews[i] = tagImageView;
			if (i == 0) {
				tagImageView.setBackgroundResource(R.drawable.page_current);
			} else {
				tagImageView.setBackgroundResource(R.drawable.page_not_current);
			}

			layout.addView(tagImageView);
		}
	}
	
	private void initViewPager() {
		viewPager = (ViewPager) findViewById(R.id.viewPager);
		viewPager.setAdapter(new MyAdapter());
		viewPager.setOnPageChangeListener(new OnPageChangeListener() {
			@Override
			public void onPageSelected(int arg0) {
				for (int i = 0; i < tagImageViews.length; i++) {
					if (i == arg0 % VIEW_NUM) {
						tagImageViews[i].setBackgroundResource(R.drawable.page_current);
					} else {
						tagImageViews[i].setBackgroundResource(R.drawable.page_not_current);
					}
				}
			}
			
			@Override
			public void onPageScrolled(int arg0, float arg1, int arg2) {
				
			}
			
			@Override
			public void onPageScrollStateChanged(int arg0) {
				
			}
		});
		viewPager.setCurrentItem(0);
	}
	
	class MyAdapter extends PagerAdapter{
		private ArrayList<View> viewList;
		public MyAdapter(){
			viewList = new ArrayList<View>();
			viewList.add(createPagerImageView(R.drawable.pic1));
			viewList.add(createPagerImageView(R.drawable.pic2));
			viewList.add(createPagerImageView(R.drawable.pic3));
			viewList.add(createPagerImageView(R.drawable.pic4));
			viewList.add(createPagerImageView(R.drawable.pic5));
		}
		
		private View createPagerImageView(int resid){
			LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
			LinearLayout layout = new LinearLayout(MainActivity.this);
			layout.setLayoutParams(params);
			layout.setOrientation(LinearLayout.VERTICAL);
			ImageView imageView = new ImageView(MainActivity.this);
			imageView.setLayoutParams(params);
			imageView.setScaleType(ScaleType.CENTER_CROP);
			imageView.setImageResource(resid);
			layout.addView(imageView);
			return layout;
		}
		
		@Override
		public int getCount() {
			return Integer.MAX_VALUE;
		}

		@Override
		public boolean isViewFromObject(View arg0, Object arg1) {
			return arg0 == arg1;
		}
		
		@Override
		public Object instantiateItem(ViewGroup container, int position) {
			((ViewPager) container).addView(viewList.get(position % VIEW_NUM),0);
			return viewList.get(position % VIEW_NUM);
		}

		@Override
		public void destroyItem(View container, int position, Object object) {
			((ViewPager) container).removeView(viewList
					.get(position % VIEW_NUM));
		}
		
	}

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

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.showviewpager"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" 
            android:theme="@android:style/Theme.Black.NoTitleBar" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>