Android 演示 ViewPager

本文内容

• 环境
• 项目结构
• 演示 1：PagerTitleStrip
• 演示 2：PagerTabStrip
• 演示 3：ViewPager 和动态 Fragment

下载 Demo

环境

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• Windows 2008 R2 64 位
• Eclipse ADT V22.6.2，Android 4.4.2（API 19）
• SAMSUNG GT-8618，Android OS 4.1.2

项目结构

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图 1 项目结构

图 2 项目主界面

演示 1：PagerTitleStrip

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演示 1 和演示 2 都是利用已有的静态的 xml 页面布局，作为 Pager 的 tab 页。通过 LayoutInflater 将 xml 布局文件，变成 View，供 ViewPager 使用。

图 3 演示 PagerTitleStrip 和点击“微博”按钮

package com.example.viewpagerdemo2.ui;

import java.util.ArrayList;

import java.util.List;

import com.example.viewpagerdemo2.R;

import com.example.viewpagerdemo2.adapter.NewPagerAdapter;

import android.os.Bundle;

import android.app.Activity;

import android.support.v4.view.PagerTitleStrip;

import android.support.v4.view.ViewPager;

import android.view.LayoutInflater;

import android.view.View;

public class PagerTitleStripDemo extends Activity {

    private View view1, view2, view3;

    private ViewPager viewPager;

    private NewPagerAdapter pagerAdapter;

    private PagerTitleStrip myPagerTitleStrip;

    private List<View> viewList;

    private List<String> titleList;

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_title);

        initClass();

        initData();

        initControl();

        initViewPager();

    }

    private void initClass() {

        viewList = new ArrayList<View>();

        titleList = new ArrayList<String>();

    }

    private void initData() {

        for (int i = 1; i <= 3; i++) {

            titleList.add(String.format("演示1页%s", i));

        }

        LayoutInflater lf = LayoutInflater.from(this);

        view1 = lf.inflate(R.layout.layout1, null);

        view2 = lf.inflate(R.layout.layout2, null);

        view3 = lf.inflate(R.layout.layout3, null);

        viewList.add(view1);

        viewList.add(view2);

        viewList.add(view3);

    }

    private void initControl() {

        viewPager = (ViewPager) findViewById(R.id.myViewPager1);

        myPagerTitleStrip = (PagerTitleStrip) findViewById(R.id.myPagerTitleStrip);

        pagerAdapter = new NewPagerAdapter(this, titleList, viewList);

    }

    private void initViewPager() {

        myPagerTitleStrip.setBackgroundColor(getResources().getColor(

                R.color.green));

        myPagerTitleStrip.setTextSpacing(50);

        viewPager.setAdapter(pagerAdapter);

    }

}

演示 2：PagerTabStrip

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图 4 演示 PagerTabStrip

package com.example.viewpagerdemo2.ui;

import java.util.ArrayList;

import java.util.List;

import com.example.viewpagerdemo2.R;

import com.example.viewpagerdemo2.adapter.NewPagerAdapter;

import android.os.Bundle;

import android.app.Activity;

import android.support.v4.view.PagerTabStrip;

import android.support.v4.view.ViewPager;

import android.view.LayoutInflater;

import android.view.View;

public class PagerTabStripDemo extends Activity {

    private View view1, view2, view3;

    private ViewPager viewPager2;

    private NewPagerAdapter pagerAdapter;

    private PagerTabStrip myPagerTabStrip;

    private List<View> viewList;

    private List<String> titleList;

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_tab);

        initClass();

        initData();

        initControl();

        initViewPager();

    }

    private void initClass() {

        viewList = new ArrayList<View>();

        titleList = new ArrayList<String>();

    }

    private void initData() {

        for (int i = 1; i <= 3; i++) {

            titleList.add(String.format("演示2页%s", i));

        }

        LayoutInflater lf = LayoutInflater.from(this);

        view1 = lf.inflate(R.layout.layout1, null);

        view2 = lf.inflate(R.layout.layout2, null);

        view3 = lf.inflate(R.layout.layout3, null);

        viewList.add(view1);

        viewList.add(view2);

        viewList.add(view3);

    }

    private void initControl() {

        viewPager2 = (ViewPager) findViewById(R.id.myViewPager2);

        myPagerTabStrip = (PagerTabStrip) findViewById(R.id.myPagerTabStrip);

        pagerAdapter = new NewPagerAdapter(this, titleList, viewList);

    }

    private void initViewPager() {

        myPagerTabStrip.setTabIndicatorColor(getResources().getColor(

                R.color.red));

        myPagerTabStrip.setDrawFullUnderline(false);

        myPagerTabStrip.setBackgroundColor(getResources().getColor(

                R.color.green));

        myPagerTabStrip.setTextSpacing(50);

        viewPager2.setAdapter(pagerAdapter);

    }

}

官方文档，对 PagerTabStrip 和 PagerTitleStrip 描述是，“PagerTabStrip is an interactive indicator of the current, next, and previous pages of a ViewPager.” 而“PagerTitleStrip is a non-interactive indicator of the current, next, and previous pages of a ViewPager. ”

简单来说，PagerTabStrip 和 PagerTitleStrip 都能实现滑动切换 Tab 页，但是 PagerTabStrip 还通过点击 Tab 的标签实现 Tab 页的切换；而 PagerTitleStrip 则不能。

下面是演示 1 和演示 2 共用的 PagerAdapter。代码如下所示：

package com.example.viewpagerdemo2.adapter;

import java.util.List;

import com.example.viewpagerdemo2.R;

import com.example.viewpagerdemo2.ui.WeiBoActivity;

import android.app.Activity;

import android.content.Intent;

import android.support.v4.view.PagerAdapter;

import android.view.View;

import android.view.View.OnClickListener;

import android.view.ViewGroup;

import android.widget.Button;

public class NewPagerAdapter extends PagerAdapter {

    private Activity activity;

    private List<String> listTitle;

    private List<View> listView;

    private Button button;

    private Intent intent;

    public NewPagerAdapter(Activity activity, List<String> title,

            List<View> view) {

        this.activity = activity;

        this.listTitle = title;

        this.listView = view;

    }

    @Override

    public int getCount() {

        return listTitle.size();

    }

    @Override

    public void destroyItem(ViewGroup container, int position, Object object) {

        container.removeView(listView.get(position));

    }

    @Override

    public int getItemPosition(Object object) {

        return super.getItemPosition(object);

    }

    @Override

    public CharSequence getPageTitle(int position) {

        return listTitle.get(position);

    }

    @Override

    public Object instantiateItem(ViewGroup container, int position) {

        container.addView(listView.get(position));

        button = (Button) container.findViewById(R.id.button1);

        button.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {

                intent = new Intent(activity, WeiBoActivity.class);

                activity.startActivity(intent);

            }

        });

        return listView.get(position);

    }

    @Override

    public boolean isViewFromObject(View arg0, Object arg1) {

        // TODO Auto-generated method stub

        return arg0 == arg1;

    }

}

ViewPager 控件都要配合一个 ***Adapter，这个 Adapter 或是 Android 提供，或是你新建 Adapter，并继承系统提供的 Adapter，然后调用 ViewPager.setAdapter 方法。

new 一个 Adapter 时，大都是将 Activity 和 adapter 构造自己需要的数据传递给他。

你会发现一个规律：只要有数据，控件就可以自己构造自己。通过 override 相应的方法，控件就知道自己的某个部分，应该利用你提供数据中的那个（些）数据。

演示 3：ViewPager 和动态 Fragment

---

动态 Fragment 在实际情况中，较为常用。

图 5 ViewPager 和动态 Fragment

package com.example.viewpagerdemo2.ui;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import com.example.viewpagerdemo2.R;

import com.example.viewpagerdemo2.adapter.NewFragmentStatePagerAdapter;

import android.os.Bundle;

import android.support.v4.app.FragmentActivity;

import android.support.v4.view.PagerTabStrip;

import android.support.v4.view.ViewPager;

public class NewFragmentActivityDemo extends FragmentActivity {

    private ViewPager mPager;

    private NewFragmentStatePagerAdapter mAdapter;

    private PagerTabStrip myPagerTabStrip;

    private List<Map<String, String>> list;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_tab);

        initClass();

        initData();

        initControl();

        initViewPager();

    }

    private void initClass() {

        list = new ArrayList<Map<String, String>>();

    }

    private void initData() {

        for (int i = 1; i <= 3; i++) {

            Map<String, String> cat = new HashMap<String, String>();

            cat.put("name", "演示3页" + i);

            cat.put("content", String.format("%s", i));

            list.add(cat);

        }

    }

    private void initControl() {

        mPager = (ViewPager) findViewById(R.id.myViewPager2);

        myPagerTabStrip = (PagerTabStrip) findViewById(R.id.myPagerTabStrip);

        mAdapter = new NewFragmentStatePagerAdapter(

                getSupportFragmentManager(), list);

    }

    private void initViewPager() {

        myPagerTabStrip.setTabIndicatorColor(getResources().getColor(

                R.color.red));

        myPagerTabStrip.setDrawFullUnderline(false);

        myPagerTabStrip.setBackgroundColor(getResources().getColor(

                R.color.green));

        myPagerTabStrip.setTextSpacing(50);

        mPager.setAdapter(mAdapter);

    }

}

自定义 Adapter，如下所示：

package com.example.viewpagerdemo2.adapter;

import java.util.List;

import java.util.Map;

import com.example.viewpagerdemo2.view.NewFragment;

import android.support.v4.app.Fragment;

import android.support.v4.app.FragmentManager;

import android.support.v4.app.FragmentStatePagerAdapter;

import android.view.ViewGroup;

public class NewFragmentStatePagerAdapter extends FragmentStatePagerAdapter {

    List<Map<String, String>> list;

    public NewFragmentStatePagerAdapter(FragmentManager fm,

            List<Map<String, String>> list) {

        super(fm);

        this.list = list;

    }

    @Override

    public int getCount() {

        return list.size();

    }

    @Override

    public CharSequence getPageTitle(int position) {

        return list.get(position).get("name");

    }

    // 初始化每个页卡选项

    @Override

    public Object instantiateItem(ViewGroup arg0, int position) {

        NewFragment ff = (NewFragment) super.instantiateItem(arg0, position);

        ff.setThings(list.get(position), position);

        return ff;

    }

    @Override

    public void destroyItem(ViewGroup container, int position, Object object) {

        System.out.println("position Destory" + position);

        super.destroyItem(container, position, object);

    }

    @Override

    public Fragment getItem(int arg0) {

        // TODO Auto-generated method stub

        return new NewFragment();

    }

}

FragmentStatePagerAdapter 和 FragmentPagerAdapter 的区别是，FragmentStatePagerAdapter 在当前只会存在前一个 Fragment，其他 Fragment 会销毁，适合加载多数据；而FragmentPagerAdapter 是所有 Fragment 都存在，所以不太适合加载大量的数据 如图片什么的，很容易内存溢出。

每个 ViewPager 里的 Fragment，如下所示：

package com.example.viewpagerdemo2.view;

import java.util.Map;

import com.example.viewpagerdemo2.R;

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;

public class NewFragment extends Fragment {

    private Map<String, String> ee;

    private int position;

    public void setThings(Map<String, String> ee, int position) {

        this.ee = ee;

        this.position = position;

    }

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

    }

    @Override

    public View onCreateView(LayoutInflater inflater, ViewGroup container,

            Bundle savedInstanceState) {

        System.out.println("onCreateView = ");

        View v = inflater.inflate(R.layout.fragment_pager, container, false);

        ((TextView) v.findViewById(R.id.myTitle)).setText(ee.get("name")

                + " = " + ee.get("content"));

        return v;

    }

    @Override

    public void onActivityCreated(Bundle savedInstanceState) {

        System.out.println("onActivityCreated = ");

        super.onActivityCreated(savedInstanceState);

    }

    @Override

    public void onDestroyView() {

        System.out.println("onDestroyView = " + position);

        super.onDestroyView();

    }

    @Override

    public void onDestroy() {

        System.out.println("onDestroy = " + position);

        super.onDestroy();

    }

}

下载 Demo