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: zhb931706659@126.com
*2014-5-3 Nanjing,njupt,China
*/
@NoTitle
@EActivity(R.layout.image_page_grid_activity)
public class ImageLoadingPageGridActivity extends FragmentActivity{

@ViewById
ViewPager pager;

PageAdapter adapter;

@AfterViews
void 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: zhb931706659@126.com
*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;
}

@Override
public 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;
}

@Override
public int getCount() {
return topics.length;
}

@Override
public CharSequence getPageTitle(int pos) {
return topics[pos];
}

@Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {

Log.d("primary", topics[position]);

ImageGridFragment fragment = (ImageGridFragment) object;
fragment.init();

}

@Override
public 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;

@Override
public 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;

}

@Override
public 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"?>

<RelativeLayout
xmlns: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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