Android中Fragment+ViewPager的配合使用

时间:2023-03-08 15:47:02
Android中Fragment+ViewPager的配合使用

官方推荐 ViewPager与Fragment一起使用,可以更加方便的管理每个Page的生命周期,这里有标准的适配器实现用于ViewPager和Fragment,涵盖最常见的用例。FragmentPagerAdapterFragmentStatePagerAdapter这两个类都有简单的代码显示如何构建一个完整的用户界面与他们。

 

适配器类:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
package com.zhf.android_viewpager_fragment;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
/**
 * 自定义fragment适配器
 * @author ZHF
 *
 */
public class MyFragmentPageAdapter extends FragmentPagerAdapter {
    public MyFragmentPageAdapter(FragmentManager fm) {
        super(fm);
    }
    @Override
    public int getCount() {
        return 3;
    }
    @Override
    public Fragment getItem(int position) {
        switch (position) {
         case 0:
                return MyFragment.newInstance(position);
            case 1:
                return MyFragment.newInstance(position);
            case 2:
                return MyFragment.newInstance(position);
            default:
                return null;
            }
    }
}

 

MyFragment类:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
package com.zhf.android_viewpager_fragment;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
/**
 * 用于创建Fragment对象,作为ViewPager的叶片
 * @author ZHF
 *
 */
public class MyFragment extends Fragment {
                                                                                                                                                                                                                                                                                                                  
    int mNum; //页号
    public static MyFragment newInstance(int num) {
        MyFragment fragment = new MyFragment();
        // Supply num input as an argument.
        Bundle args = new Bundle();
        args.putInt("num", num);
        fragment.setArguments(args);
        return fragment;
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //这里我只是简单的用num区别标签,其实具体应用中可以使用真实的fragment对象来作为叶片
        mNum = getArguments() != null ? getArguments().getInt("num") : 1;
    }
    /**为Fragment加载布局时调用**/
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
                                                                                                                                                                                                                                                                                                                      
        View view = inflater.inflate(R.layout.fragment_pager_list, null);
        TextView tv = (TextView) view.findViewById(R.id.text);
        tv.setText("fragment+" + mNum);
        return view;
    }
}

 

布局文件:

 

activity_main.xml

1
2
3
4
5
6
7
8
9
10
<RelativeLayout 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.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />
</RelativeLayout>

fragment_pager_list.xml

1
2
3
4
5
6
7
8
9
10
11
12
13
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:drawable/gallery_thumb"
    android:orientation="vertical" >
    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_vertical|center_horizontal"
        android:text="@string/hello_world"
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>

 

MainActivity类:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
package com.zhf.android_viewpager_fragment;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.view.ViewPager;
public class MainActivity extends FragmentActivity {
    private ViewPager mViewPager;
    private MyFragmentPageAdapter mAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mViewPager = (ViewPager) findViewById(R.id.viewpager);
                                                                                                                                                                                                                                 
        //这里因为是3.0一下版本,所以需继承FragmentActivity,通过getSupportFragmentManager()获取FragmentManager
        //3.0及其以上版本,只需继承Activity,通过getFragmentManager获取事物
        FragmentManager fm = getSupportFragmentManager();
        //初始化自定义适配器
        mAdapter =  new MyFragmentPageAdapter(fm);
        //绑定自定义适配器
        mViewPager.setAdapter(mAdapter);
    }
}

 

效果图:

Android中Fragment+ViewPager的配合使用

效果与ViewPager中添加View的效果是一样的!但是它与View的区别在于它有自己的生命周期,可以随时更改自己的状态便于管理。

 

事实上使用FragmentPagerAdapter 时,Fragment对象会一直存留在内存中,所以当有大量的显示页时,就不适合用FragmentPagerAdapter了,FragmentPagerAdapter 适用于只有少数的page情况,像选项卡。

这个时候你可以考虑使用FragmentStatePagerAdapter ,当使用FragmentStatePagerAdapter 时,如果Fragment不显示,那么Fragment对象会被销毁,(滑过后会保存当前界面,以及下一个界面和上一个界面(如果有),最多保存3个,其他会被销毁掉)
但在回调onDestroy()方法之前会回调onSaveInstanceState(Bundle outState)方法来保存Fragment的状态,下次Fragment显示时通过onCreate(Bundle savedInstanceState)把存储的状态值取出来,FragmentStatePagerAdapter
 比较适合页面比较多的情况,像一个页面的ListView 。

原文 http://smallwoniu.blog.51cto.com/3911954/1322746