ViewPager之欢迎界面

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ViewPager是android扩展包v4包中的类，这个类可以让用户左右切换当前的view。

下面我们先简单介绍一下ViewPager

1.ViewPager类直接继承了ViewGroup类，所有它是一个容器类，可以在其中添加其他的view类。

2.ViewPager类需要一个PagerAdapter适配器类给它提供数据。

3.ViewPager经常和Fragment一起使用，并且提供了专门的FragmentPagerAdapter和FragmentStatePagerAdapter类供Fragment中的ViewPager使用。（这个今天的应用暂时用不到）

下面我们开始看代码

activity_main.xml

<?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:orientation="vertical" >    <RelativeLayout        android:id="@+id/mylovemodelactivity_myframelayout"        android:layout_width="wrap_content"        android:layout_height="wrap_content" >        <android.support.v4.view.ViewPager            android:id="@+id/helpcentershowactivity_vp"            android:layout_width="fill_parent"            android:layout_height="fill_parent" />        <!-- 最后页面跳转按钮 -->        <Button            android:id="@+id/ljtyButton"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_above="@+id/gallery_page"            android:layout_centerHorizontal="true"            android:layout_gravity="center"            android:layout_marginBottom="10dp"            android:background="@drawable/at_once_go"            android:visibility="invisible" />        <!-- 进度小圆点 -->        <LinearLayout            android:id="@+id/gallery_page"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:layout_alignParentBottom="true"            android:gravity="center_horizontal"            android:orientation="horizontal"            android:paddingBottom="20dp" >            <ImageView                android:id="@+id/newguideactivity_dot_0"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_marginLeft="5dip"                android:layout_marginRight="5dip"                android:src="@drawable/point_down" />            <ImageView                android:id="@+id/newguideactivity_dot_1"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_marginLeft="5dip"                android:layout_marginRight="5dip"                android:src="@drawable/point_up" />            <ImageView                android:id="@+id/newguideactivity_dot_2"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_marginLeft="5dip"                android:layout_marginRight="5dip"                android:src="@drawable/point_up" />            <ImageView                android:id="@+id/newguideactivity_dot_3"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_marginLeft="5dip"                android:layout_marginRight="5dip"                android:src="@drawable/point_up" />            <ImageView                android:id="@+id/newguideactivity_dot_4"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_marginLeft="5dip"                android:layout_marginRight="5dip"                android:src="@drawable/point_up" />        </LinearLayout>    </RelativeLayout></LinearLayout>

GalleryAdapter.java

package com.yitong.viewpagerdemo;import java.io.InputStream;import java.util.ArrayList;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.drawable.BitmapDrawable;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.view.View;import android.view.ViewGroup;import android.view.ViewGroup.LayoutParams;import android.widget.Gallery;import android.widget.ImageView;public class GalleryAdapter extends PagerAdapter {private String[] picNames;private ArrayList<ImageView> images = null;private Context context = null;/** * 通过名称读取image 避免一次加载过多造成内存溢出 *  */@SuppressWarnings("deprecation")public GalleryAdapter(Context ctx, String[] picNames) {this.context = ctx;this.picNames = picNames;images = new ArrayList<ImageView>();for (int i = 0; i < picNames.length; i++) {ImageView imageView = new ImageView(context);imageView.setScaleType(ImageView.ScaleType.FIT_XY);imageView.setLayoutParams(new Gallery.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));try {InputStream assetFile = null;// 默认加载第0个assetFile = context.getAssets().open(picNames[i]);// 用来存储图片资源 仅仅创建一个，过度即时销毁Bitmap imgBitMap;BitmapDrawable bd;imgBitMap = BitmapFactory.decodeStream(assetFile);bd = new BitmapDrawable(context.getResources(), imgBitMap);imageView.setBackgroundDrawable(bd);} catch (Exception e) {e.printStackTrace();}images.add(imageView);}}@Overridepublic int getCount() {// TODO Auto-generated method stubreturn picNames.length;}@Overridepublic boolean isViewFromObject(View arg0, Object arg1) {// TODO Auto-generated method stubreturn arg0 == arg1;}@Overridepublic Object instantiateItem(ViewGroup view, int position) {view.addView(images.get(position % picNames.length));return images.get(position % picNames.length);}@Overridepublic void destroyItem(ViewGroup view, int position, Object object) {// 从viewpager里移除childviewview.removeView(images.get(position % picNames.length));}/** * 清空刷新內存 *  * @Description */public void clearHeap() {if (picNames != null && picNames.length > 0) {try {for (int i = 0; i < images.size(); i++) {BitmapDrawable bd = (BitmapDrawable) images.get(i).getBackground();images.get(i).setBackgroundResource(0);// 别忘了把背景设为null，避免onDraw刷新背景时候出现used// a recycled// bitmap错误bd.setCallback(null);bd.getBitmap().recycle();}// 清空内存System.gc();} catch (Exception e) {e.printStackTrace();}}}}

MainActivity.java

package com.yitong.viewpagerdemo;import java.util.ArrayList;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.OnPageChangeListener;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ImageView;public class MainActivity extends Activity implements OnClickListener {private ArrayList<ImageView> dots;private ViewPager viewPager;private GalleryAdapter madapter;private Button ljtyButton;// 图片资源名称数组private String[] picNames;private void inintPictureArray() {picNames = new String[] { "gallery_1.png", "gallery_2.png","gallery_3.png", "gallery_4.png", "gallery_5.png" };}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);inintPictureArray();initAd();ljtyButton = (Button) findViewById(R.id.ljtyButton);ljtyButton.setOnClickListener(this);}@Overridepublic void onClick(View v) {// 跳转事件 当页面到最后的时候出现按钮进行跳转if (v == ljtyButton) {Intent intent = new Intent(this, WeclomeActivity.class);intent.putExtra("ISFRIST", true);startActivity(intent);finish();madapter.clearHeap();}}private boolean isChange = false;private ImageView dot_0;private ImageView dot_1;private ImageView dot_2;private ImageView dot_3;private ImageView dot_4;@SuppressWarnings("deprecation")public void initAd() {// 将下面的进度图片放在list中dots = new ArrayList<ImageView>();dot_0 = (ImageView) findViewById(R.id.newguideactivity_dot_0);dot_1 = (ImageView) findViewById(R.id.newguideactivity_dot_1);dot_2 = (ImageView) findViewById(R.id.newguideactivity_dot_2);dot_3 = (ImageView) findViewById(R.id.newguideactivity_dot_3);dot_4 = (ImageView) findViewById(R.id.newguideactivity_dot_4);dots.add(dot_0);dots.add(dot_1);dots.add(dot_2);dots.add(dot_3);dots.add(dot_4);viewPager = (ViewPager) findViewById(R.id.helpcentershowactivity_vp);madapter = new GalleryAdapter(this, picNames);viewPager.setAdapter(madapter);// viewPager.setOnTouchListener(this);viewPager.setOnPageChangeListener(new OnPageChangeListener() {int oldPosition = 0;// 滑动监听public void onPageSelected(int position) {dots.get(position % picNames.length).setImageResource(R.drawable.point_down);dots.get(oldPosition).setImageResource(R.drawable.point_up);oldPosition = position % picNames.length;// 当欢迎页面滑倒最后一行 显示跳转按钮if (position == 4) {isChange = true;ljtyButton.setVisibility(View.VISIBLE);} else {isChange = false;ljtyButton.setVisibility(View.INVISIBLE);}}public void onPageScrolled(int position, float arg1, int arg2) {}public void onPageScrollStateChanged(int position) {}});}}

Demo下载连接

http://download.csdn.net/detail/daniu52100/9482183

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