android控件篇：ViewPager+Fragment+GridView的使用（与AndroidQuery框架结合）

最近看了一个AndroidQuery的框架，里面的Demo，有个界面，让博主很喜欢。左右滑动十分顺畅，手感很好，于是拿来和大家分享一下。先看一下效果图：

从图中可以看出，上面的布局是一个Layout里面嵌套有个ViewPager，ViewPager中包含着Fragment，Fragment的布局文件包含了一个简单的GridView，GridView的Item布局很简单，就是一个100*100大小的图片。好啦，先说这么多，然后咱们看代码吧。

最外层Activity的布局文件

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <TextView        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:gravity="center"        android:text="Display 10x100 images from Picasa." />    <android.support.v4.view.ViewPager        android:id="@+id/pager"        android:layout_width="fill_parent"        android:layout_height="fill_parent" >        <android.support.v4.view.PagerTabStrip            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_gravity="top" />    </android.support.v4.view.ViewPager></LinearLayout>

相应的Activity的java文件：（使用了AndroidAnnotation框架）

/* * $filename: ImageLoadingPageGridActivity.java,v $ * $Date: 2014-5-3  $ * Copyright (C) ZhengHaibo, Inc. All rights reserved. * This software is Made by Zhenghaibo. */package edu.njupt.zhb;import org.androidannotations.annotations.AfterViews;import org.androidannotations.annotations.EActivity;import org.androidannotations.annotations.NoTitle;import org.androidannotations.annotations.ViewById;import android.support.v4.app.FragmentActivity;import android.support.v4.view.ViewPager;/* *@author: ZhengHaibo *web:     http://blog.csdn.net/nuptboyzhb *mail:    [e-mail] *2014-5-3  Nanjing,njupt,China */@NoTitle@EActivity(R.layout.image_page_grid_activity)public class ImageLoadingPageGridActivity extends FragmentActivity{@ViewByIdViewPager pager;PageAdapter adapter;@AfterViewsvoid afterViews(){adapter = new PageAdapter(getSupportFragmentManager(),ImageLoadingPageGridActivity.this);pager.setAdapter(adapter);pager.setOffscreenPageLimit(3);//设置缓存视图的数目}}

大家注意：setOffscreenPageLimit的参数设置，数目越大，缓存的越多，切换的时候，加载的越快。但，并不是越大越好，内存中缓存的越多，消耗的手机资源就越多。

下面看一下PageAdapter的代码

/* * $filename: PageAdapter.java,v $ * $Date: 2014-5-3  $ * Copyright (C) ZhengHaibo, Inc. All rights reserved. * This software is Made by Zhenghaibo. */package edu.njupt.zhb;import android.content.Context;import android.os.Bundle;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentStatePagerAdapter;import android.util.Log;import android.view.ViewGroup;/* *@author: ZhengHaibo   *web:     http://blog.csdn.net/nuptboyzhb *mail:    [e-mail] *2014-5-3  Nanjing,njupt,China */public class PageAdapter extends FragmentStatePagerAdapter {private static String[] topics = { "dog", "cat", "bird", "panda", "horse","elephant", "bear", "butterfly", "monkey", "fish", "tiger","chicken", "pig" };Context context;public PageAdapter(FragmentManager fm, Context context) {super(fm);this.context = context;}@Overridepublic Fragment getItem(int pos) {Log.d("primary", topics[pos]);Bundle args = new Bundle();args.putString("topic", topics[pos]);ImageGridFragment fragment = (ImageGridFragment) Fragment.instantiate(context, ImageGridFragment.class.getName(), args);return fragment;}@Overridepublic int getCount() {return topics.length;}@Overridepublic CharSequence getPageTitle(int pos) {return topics[pos];}@Overridepublic void setPrimaryItem(ViewGroup container, int position, Object object) {Log.d("primary", topics[position]);ImageGridFragment fragment = (ImageGridFragment) object;fragment.init();}@Overridepublic void destroyItem(ViewGroup container, int position, Object object) {Log.d("destroyItem", topics[position]);}}

从上面的额PageAdapter的代码可以看出，里面总共有13个页面。也就是左右滑动的时候，有13个Fragment。这里，注意一下getItem方法，它返回的是一个ImageGridFragment，并且向该Fragment中传递了键为topic的键值对。

下面看一下对应的ImageGridFragment的java文件和布局文件：

package edu.njupt.zhb;import java.util.ArrayList;import java.util.List;import android.os.Bundle;import android.support.v4.app.Fragment;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ArrayAdapter;import com.androidquery.AQuery;import com.androidquery.callback.AjaxStatus;import com.androidquery.util.AQUtility;import com.androidquery.util.XmlDom;public class ImageGridFragment extends Fragment {private AQuery aq;private AQuery aq2;private String topic;private List<Photo> photos;@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {View view = inflater.inflate(R.layout.image_grid_fragment, container,false);aq = new AQuery(getActivity(), view);aq2 = new AQuery(getActivity());Log.d("ViewPagerDemo","onCreateView...");return view;}@Overridepublic void onActivityCreated(Bundle savedInstanceState) {super.onActivityCreated(savedInstanceState);topic = getArguments().getString("topic");Log.d("ViewPagerDemo","onActivityCreated...");}private boolean inited;public void init() {if (aq == null || inited)return;inited = true;Log.d("ViewPagerDemo","init...");refresh();}public void refresh() {ajaxPhotos();}private void ajaxPhotos() {String url = "https://picasaweb.google.com/data/feed/api/all?q="+ topic + "&max-results=100";aq.progress(R.id.progress).ajax(url, XmlDom.class, 0, this, "photosCb");}public void photosCb(String url, XmlDom xml, AjaxStatus status) {if (xml != null) {photos = convertAll(xml);render(photos);}}private void render(List<Photo> entries) {AQUtility.debug("render setup");ArrayAdapter<Photo> aa = new ArrayAdapter<Photo>(getActivity(),R.layout.grid_item2, entries) {public View getView(int position, View convertView, ViewGroup parent) {if (convertView == null) {convertView = aq.inflate(convertView, R.layout.grid_item2,parent);}Photo photo = getItem(position);AQuery aq = aq2.recycle(convertView);String tbUrl = photo.tb;if (aq.shouldDelay(position, convertView, parent, tbUrl)) {aq.id(R.id.tb).clear();} else {aq.id(R.id.tb).image(tbUrl, true, true, 200,R.drawable.image_missing, null, 0, 0);}return convertView;}};aq.id(R.id.grid).adapter(aa);}private List<Photo> convertAll(XmlDom xml) {List<XmlDom> entries = xml.children("entry");List<Photo> result = new ArrayList<Photo>();for (XmlDom entry : entries) {result.add(convert(entry));}return result;}private Photo convert(XmlDom xml) {String url = xml.child("content").attr("src");String title = xml.child("title").text();String author = xml.child("author").text("name");String tb = url;List<XmlDom> tbs = xml.tags("media:thumbnail");if (tbs.size() > 0) {// tb = tbs.get(0).attr("url");tb = tbs.get(tbs.size() - 1).attr("url");}tb = tb.replaceAll("https:", "http:");Photo photo = new Photo();photo.url = url;photo.tb = tb;photo.title = title;photo.author = author;return photo;}class Photo {String tb;String url;String title;String author;}}

布局文件

<?xml version="1.0" encoding="utf-8"?><RelativeLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="fill_parent"android:orientation="vertical">    <GridView     android:id="@+id/grid"    android:layout_width="fill_parent"     android:layout_height="fill_parent"    android:columnWidth="90dp"    android:numColumns="auto_fit"    android:verticalSpacing="10dp"    android:horizontalSpacing="10dp"    android:stretchMode="columnWidth"    android:gravity="center"/>        <ProgressBar         android:id="@+id/progress"    android:layout_width="wrap_content"     android:layout_height="wrap_content"        android:layout_centerInParent="true"        android:visibility="gone"        /></RelativeLayout>

注意：ImageGridFragment的init方法是在PageAdapter中调用的。本Demo中，init是直接使用AQuery从网络上获取相应的资源。而对于实际的项目，我们首先检查本地数据库是否有相应的资源，如果有，先加载。其次，向网络中获取，查看是否有更新，如有更新，就再在原来的基础上，添加数据。

整个项目中得比较关键的布局就这么多。整个项目下载地址：http://download.csdn.net/detail/nuptboyzhb/7287219

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