viewpager的简单使用，以及ValueAnimator的用法示例

之前在网上看到一篇viewpager简单使用的例子程序，主要采用了上部标签button+中间指示作用的imageview+下部viewpager的结构，点击上部标签，或者滑动viewpager，均可以使中间的imageview产生滑动效果，但是由于程序不够完善，当改变imageview背景等时，不能够正确的显示我们期望的UI效果，因此我对此进行了优化，同时去掉原示例中使用的animation，转而采用valueanimator+imageview的matrix方法进行编码，解决了之前UI中体现的BUG,当然远远不能说满意，权当是对viewpager、valueanimator理解的入门示例。

注：以下编码对网上的示例程序多有借鉴，但是出处找不到了

  1 package com.example.testandroidviewpager;
  2 
  3 import java.util.ArrayList;
  4 import java.util.List;
  5 
  6 import android.animation.ValueAnimator;
  7 import android.app.Activity;
  8 import android.graphics.BitmapFactory;
  9 import android.graphics.Matrix;
 10 import android.os.Bundle;
 11 import android.os.Parcelable;
 12 import android.support.v4.view.PagerAdapter;
 13 import android.support.v4.view.ViewPager;
 14 import android.support.v4.view.ViewPager.OnPageChangeListener;
 15 import android.util.DisplayMetrics;
 16 import android.util.Log;
 17 import android.view.LayoutInflater;
 18 import android.view.View;
 19 import android.view.animation.AccelerateInterpolator;
 20 import android.view.animation.Animation;
 21 import android.view.animation.BounceInterpolator;
 22 import android.view.animation.TranslateAnimation;
 23 import android.widget.ImageView;
 24 import android.widget.TextView;
 25 
 26 public class MainActivity extends Activity {
 27 
 28     private ViewPager mPager;//页卡内容
 29     private List<View> listViews; // Tab页面列表
 30     private ImageView cursor;// 动画图片
 31     private TextView t1, t2, t3;// 页卡头标
 32     private int offset = 0;// 动画图片偏移量
 33     private int currIndex = 0;// 当前页卡编号
 34     private int prevIndex = 0;// 移动前页卡编号
 35     private int bmpW;// 动画图片宽度
 36     private int screenW;//屏幕宽度，由于只是示例因此简单起见，直接使用屏幕宽度
 37     @Override
 38     protected void onCreate(Bundle savedInstanceState) {
 39         super.onCreate(savedInstanceState);
 40         setContentView(R.layout.activity_main);
 41         InitTextView();
 42         InitImageView();
 43         InitViewPager();
 44     }
 45 
 46     /**
 47      * 初始化头标
 48      */
 49     private void InitTextView() {
 50         t1 = (TextView) findViewById(R.id.text1);
 51         t2 = (TextView) findViewById(R.id.text2);
 52         t3 = (TextView) findViewById(R.id.text3);
 53 
 54         t1.setOnClickListener(new MyOnClickListener(0));
 55         t2.setOnClickListener(new MyOnClickListener(1));
 56         t3.setOnClickListener(new MyOnClickListener(2));
 57     }
 58 
 59     /**
 60      * 头标点击监听
 61      */
 62     public class MyOnClickListener implements View.OnClickListener {
 63         private int index = 0;
 64 
 65         public MyOnClickListener(int i) {
 66             index = i;
 67         }
 68 
 69         @Override
 70         public void onClick(View v) {
 71             mPager.setCurrentItem(index);
 72         }
 73     };
 74     
 75     /**
 76      * 初始化ViewPager
 77      */
 78     private void InitViewPager() {
 79         mPager = (ViewPager) findViewById(R.id.vPager);
 80         listViews = new ArrayList<View>();
 81         LayoutInflater mInflater = getLayoutInflater();
 82         listViews.add(mInflater.inflate(R.layout.page0, null));
 83         listViews.add(mInflater.inflate(R.layout.page1, null));
 84         listViews.add(mInflater.inflate(R.layout.page2, null));
 85         mPager.setAdapter(new MyPagerAdapter(listViews));
 86         mPager.setCurrentItem(0);
 87         mPager.setOnPageChangeListener(new MyOnPageChangeListener());
 88     }
 89     
 90     /**
 91      * ViewPager适配器
 92      */
 93     public class MyPagerAdapter extends PagerAdapter {
 94         public List<View> mListViews;
 95 
 96         public MyPagerAdapter(List<View> mListViews) {
 97             this.mListViews = mListViews;
 98         }
 99 
100         @Override
101         public void destroyItem(View arg0, int arg1, Object arg2) {
102             ((ViewPager) arg0).removeView(mListViews.get(arg1));
103         }
104 
105         @Override
106         public void finishUpdate(View arg0) {
107         }
108 
109         @Override
110         public int getCount() {
111             return mListViews.size();
112         }
113 
114         @Override
115         public Object instantiateItem(View arg0, int arg1) {
116             ((ViewPager) arg0).addView(mListViews.get(arg1), 0);
117             return mListViews.get(arg1);
118         }
119 
120         @Override
121         public boolean isViewFromObject(View arg0, Object arg1) {
122             Log.d("1202","view pager isViewFromObject --> return " + (arg0 == arg1));
123             return arg0 == arg1;
124         }
125 
126         @Override
127         public void restoreState(Parcelable arg0, ClassLoader arg1) {
128         }
129 
130         @Override
131         public Parcelable saveState() {
132             return null;
133         }
134 
135         @Override
136         public void startUpdate(View arg0) {
137         }
138     }
139     
140     /**
141      * 初始化动画
142      */
143     private void InitImageView() {
144         cursor = (ImageView) findViewById(R.id.cursor);
145         bmpW = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher)
146                 .getWidth();// 获取图片宽度
147         DisplayMetrics dm = new DisplayMetrics();
148         getWindowManager().getDefaultDisplay().getMetrics(dm);
149         screenW = dm.widthPixels;// 获取分辨率宽度
150         offset = (screenW / 3 - bmpW) / 2;// 计算偏移量
151         Matrix matrix = new Matrix();
152         matrix.postTranslate(offset, 0);
153         cursor.setImageMatrix(matrix);// 设置动画初始位置
154     }
155     
156     
157     /**
158      * 页卡切换监听
159      */
160     public class MyOnPageChangeListener implements OnPageChangeListener {
161 
162         int one = screenW / 3;// 页卡1 -> 页卡2 偏移量//==screenw/3
163         int two = one * 2;// 页卡1 -> 页卡3 偏移量
164 
165         @Override
166         public void onPageSelected(int arg0) {
167 
168             Animation animation = null;
169             switch (arg0) {
170             case 0:
171                 if (currIndex == 1) {
172                     animation = new TranslateAnimation(one, 0, 0, 0);
173                 } else if (currIndex == 2) {
174                     animation = new TranslateAnimation(two, 0, 0, 0);
175                 }
176                 break;
177             case 1:
178                 if (currIndex == 0) {
179                     animation = new TranslateAnimation(0, one, 0, 0);
180                 } else if (currIndex == 2) {
181                     animation = new TranslateAnimation(two, one, 0, 0);
182                 }
183                 break;
184             case 2:
185                 if (currIndex == 0) {
186                     animation = new TranslateAnimation(0, two, 0, 0);
187                 } else if (currIndex == 1) {
188                     animation = new TranslateAnimation(one, two, 0, 0);
189                 }
190                 break;
191             }
192             final Matrix matrix = new Matrix();
193             prevIndex = currIndex;
194             currIndex = arg0;
195             
196             ValueAnimator animator0 = ValueAnimator.ofFloat(0f, 1f);
197             animator0.setDuration(300);
198 //            animator0.setInterpolator(new BounceInterpolator());
199             animator0.setInterpolator(new AccelerateInterpolator(2));
200             animator0.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
201                 
202                 @Override
203                 public void onAnimationUpdate(ValueAnimator animation) {
204                     Object o = animation.getAnimatedValue();
205                     if(o != null){
206                         float f = (Float)o;
207                         Log.d("1201", "onAnimationUpdate f is " + f);
208                         //prevIndex --> currIndex
209                         matrix.reset();
210                         int prevX = offset + one * prevIndex;
211                         int currX = offset + one * currIndex;
212                         int nowValue = (int) (prevX + f * (currX - prevX));
213                         matrix.postTranslate(nowValue, 0);
214                         cursor.setImageMatrix(matrix);
215                     }
216                 }
217             });
218             animator0.start();
219             
220             cursor.setImageMatrix(matrix);// 设置动画初始位置
221             
222 //            animation.setFillAfter(true);// True:图片停在动画结束位置
223 //            animation.setDuration(300);
224 //            cursor.startAnimation(animation);
225         }
226 
227         @Override
228         public void onPageScrolled(int arg0, float arg1, int arg2) {
229         }
230 
231         @Override
232         public void onPageScrollStateChanged(int arg0) {
233         }
234     }
235     
236 }

layout：activity_main.xml

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     xmlns:umadsdk="http://schemas.android.com/apk/res/com.LoveBus"
 4     android:layout_width="fill_parent"
 5     android:layout_height="fill_parent"
 6     android:orientation="vertical" >
 7 
 8     <LinearLayout
 9         android:id="@+id/linearLayout1"
10         android:layout_width="fill_parent"
11         android:layout_height="100.0dip"
12         android:background="#FFFFFF" >
13 
14         <TextView
15             android:id="@+id/text1"
16             android:layout_width="fill_parent"
17             android:layout_height="fill_parent"
18             android:layout_weight="1.0"
19             android:gravity="center"
20             android:text="页卡1"
21             android:textColor="#000000"
22             android:textSize="22.0dip" />
23 
24         <TextView
25             android:id="@+id/text2"
26             android:layout_width="fill_parent"
27             android:layout_height="fill_parent"
28             android:layout_weight="1.0"
29             android:gravity="center"
30             android:text="页卡2"
31             android:textColor="#000000"
32             android:textSize="22.0dip" />
33 
34         <TextView
35             android:id="@+id/text3"
36             android:layout_width="fill_parent"
37             android:layout_height="fill_parent"
38             android:layout_weight="1.0"
39             android:gravity="center"
40             android:text="页卡3"
41             android:textColor="#000000"
42             android:textSize="22.0dip" />
43     </LinearLayout>
44 
45     <ImageView
46         android:id="@+id/cursor"
47         android:background="#333333"
48         android:layout_width="fill_parent"
49         android:layout_height="wrap_content"
50         android:scaleType="matrix"
51         android:src="@drawable/ic_launcher" />
52 
53     <android.support.v4.view.ViewPager
54         android:id="@+id/vPager"
55         android:layout_width="wrap_content"
56         android:layout_height="wrap_content"
57         android:layout_gravity="center"
58         android:layout_weight="1.0"
59         android:background="#000000"
60         android:flipInterval="30"
61         android:persistentDrawingCache="animation" />
62 
63 </LinearLayout>
page0.xml
1 <?xml version="1.0" encoding="utf-8"?>
2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3     android:layout_width="match_parent"
4     android:layout_height="match_parent"
5     android:background="#330000"
6     android:orientation="vertical" >
7 
8 </LinearLayout>

page1.xml

1 <?xml version="1.0" encoding="utf-8"?>
2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3     android:layout_width="match_parent"
4     android:layout_height="match_parent"
5     android:background="#003300"
6     android:orientation="vertical" >
7 
8 </LinearLayout>

page2.xml

1 <?xml version="1.0" encoding="utf-8"?>
2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3     android:layout_width="match_parent"
4     android:layout_height="match_parent"
5     android:background="#000033"
6     android:orientation="vertical" >
7 
8 </LinearLayout>

注意：位于界面中间的imageview，其scaletype一定要设置成为matrix。

原理：主要是使用valueanimator对matrix的

postTranslate()函数的参数进行了设置，然后不断更新imageview，使其具有动画效果。
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原文地址：https://www.cnblogs.com/carbs/p/5010661.html