FragmentPagerAdapter 适合只有少量的pager，所有pager同时全部存在，不会有被销毁的，page过多很容易内存溢出.
1，代码
1.1 ViewPagerMain.java
1 import android.os.Bundle;
2 import android.support.v4.app.Fragment;
3 import android.support.v4.view.ViewPager;
4 import android.view.LayoutInflater;
5 import android.view.View;
6 import android.view.ViewGroup;
7
8 import com.txw.e.viewpager.R;
9
10 public class ViewPagerMain extends Fragment {
11
12 //1，在layout.xml中添加 ViewPagerFragment,它可以是顶级布局，如下：
13 /*
14 <?xml version="1.0" encoding="utf-8"?>
15 <android.support.v4.view.ViewPagerFragment
16 android:id="@+id/view_pager"
17 xmlns:android="http://schemas.android.com/apk/res/android"
18 android:layout_width="match_parent"
19 android:layout_height="match_parent"/>
20 */
21
22 //2，准备变量,ViewPager和 PagerAdapter ,OnPageChangeListener
23 ViewPager pager;
24 ViewPagerAdapter pagerAdapter;
25 ViewPager.SimpleOnPageChangeListener simpleOnPageChangeListener;
26
27 //3，初始化pager
28 void initPager(View v){
29 //从layout.xml中初始化pager
30 pager = (ViewPager) v.findViewById(R.id.view_pager);
31
32 //初始化page adapter
33 pagerAdapter = new ViewPagerAdapter(getFragmentManager());
34
35 //设置adapter
36 pager.setAdapter(pagerAdapter);
37
38 //设置page切换监听者
39 simpleOnPageChangeListener = new ViewPager.SimpleOnPageChangeListener();
40 pager.addOnPageChangeListener(simpleOnPageChangeListener);
41
42 //设置pager切换动画
43 pager.setPageTransformer(true, new DepthPageTransformer());
44
45
46 }
47
48 //4，处理 pager 切换事件
49 //这里用的ViewPager.SimpleOnPageChangeListener,它什么也不做。
50
51 //5，重写切换动画类，可以把这个类放到外面去。
52 public class DepthPageTransformer implements ViewPager.PageTransformer {
53 private static final float MIN_SCALE = 0.75f;
54
55 public void transformPage(View view, float position) {
56 int pageWidth = view.getWidth();
57
58 if (position < -1) { // [-Infinity,-1)
59 // This page is way off-screen to the left.
60 view.setAlpha(0);
61
62 } else if (position <= 0) { // [-1,0]
63 // Use the default slide transition when moving to the left page
64 view.setAlpha(1);
65 view.setTranslationX(0);
66 view.setScaleX(1);
67 view.setScaleY(1);
68
69 } else if (position <= 1) { // (0,1]
70 // Fade the page out.
71 view.setAlpha(1 - position);
72
73 // Counteract the default slide transition
74 view.setTranslationX(pageWidth * -position);
75
76 // Scale the page down (between MIN_SCALE and 1)
77 float scaleFactor = MIN_SCALE
78 + (1 - MIN_SCALE) * (1 - Math.abs(position));
79 view.setScaleX(scaleFactor);
80 view.setScaleY(scaleFactor);
81
82 } else { // (1,+Infinity]
83 // This page is way off-screen to the right.
84 view.setAlpha(0);
85 }
86 }
87 }
88
89 @Override
90 public View onCreateView(LayoutInflater inflater, ViewGroup container,
91 Bundle savedInstanceState) {
92 // Inflate the layout for this fragment
93 View v = inflater.inflate(R.layout.fragment_pager_main, container, false);
94
95 initPager(v);
96
97 return v;
98 }
99 }
1.2 ViewPagerAdapter.java
1 import android.os.Bundle;
2 import android.support.v4.app.Fragment;
3 import android.support.v4.app.FragmentManager;
4 import android.support.v4.app.FragmentPagerAdapter;
5
6 public class ViewPagerAdapter extends FragmentPagerAdapter{
7
8 /*
9 适合只有少量的pager，所有pager同时全部存在，不会有被销毁的，page过多很容易内存溢出.
10 */
11 public ViewPagerAdapter(FragmentManager fm) {
12 super(fm);
13 }
14
15 @Override
16 public Fragment getItem(int position) {
17 System.out.println("getItem:create fragment");
18 ViewPagerFragment fragment = new ViewPagerFragment();
19 Bundle args = new Bundle();
20 args.putInt("ID",position);
21 fragment.setArguments(args);
22 return fragment;
23 }
24
25 @Override
26 public int getCount() {
27 return 5;
28 }
29 }
1.3 ViewPagerFragment.java
1 import android.os.Bundle;
2 import android.support.v4.app.Fragment;
3 import android.view.LayoutInflater;
4 import android.view.View;
5 import android.view.ViewGroup;
6 import android.widget.TextView;
7
8 import com.txw.e.viewpager.R;
9
10 public class ViewPagerFragment extends Fragment {
11
12
13 @Override
14 public void onCreate(Bundle savedInstanceState) {
15 super.onCreate(savedInstanceState);
16 System.out.println("ViewPagerFragment" + getArguments().getInt("ID") + "::onCreate()");
17 }
18
19 @Override
20 public View onCreateView(LayoutInflater inflater, ViewGroup container,
21 Bundle savedInstanceState) {
22 // Inflate the layout for this fragment
23 View v = inflater.inflate(R.layout.fragment_pager, container, false);
24 TextView tv = (TextView) v.findViewById(R.id.view_pager_content);
25 Bundle args = getArguments();
26 int position = args.getInt("ID");
27 tv.setText("ViewPagerFragment " + position);
28 v.setTranslationX(-1 * v.getWidth() * position);
29 return v;
30 }
31
32 @Override
33 public void onDestroy() {
34 super.onDestroy();
35 System.out.println("ViewPagerFragment" + getArguments().getInt("ID") + "::onDestroy()");
36 }
37
38 }
2，xml
2.1 fragment_pager_main.xml
1 <?xml version="1.0" encoding="utf-8"?>
2 <android.support.v4.view.ViewPager
3 android:id="@+id/view_pager"
4 xmlns:android="http://schemas.android.com/apk/res/android"
5 android:background="#FFFFFF"
6 android:layout_width="match_parent"
7 android:layout_height="match_parent"/>
2.2 fragment_pager.xml
1 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
2 xmlns:tools="http://schemas.android.com/tools"
3 android:layout_width="match_parent"
4 android:layout_height="match_parent"
5 android:background="#FFFFFF"
6 tools:context=".ViewPager.ViewPagerFragment">
7
8 <TextView
9 android:id="@+id/view_pager_txt"
10 android:layout_width="match_parent"
11 android:layout_height="wrap_content"
12 android:text="适合只有少量的pager，所有pager同时全部存在，不会有被销毁的，page过多很容易内存溢出.\n可以在LogCat中查看page对应的Fragment\n的onCreate,onDestory"/>
13
14 <TextView
15 android:id="@+id/view_pager_content"
16 android:layout_width="match_parent"
17 android:layout_height="match_parent"
18 android:gravity="center_horizontal|center_vertical"
19 android:text="@string/hello_blank_fragment"/>
20
21 </FrameLayout>
