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

---

• 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

---

图 1 项目结构

图 2 项目主界面 

演示 1：PagerTitleStrip

---

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

---

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