Android程序开发ListView+Json+异步网络图片加载+滚动翻页的例子（图片能缓存，图片不错乱）_Android

例子中用于解析Json的Gson请自己Google下载

主Activity：

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									package COM.Example.Main;

									import java.util.HashMap;

									import java.util.Iterator;

									import java.util.LinkedList;

									import java.util.List;

									import java.util.Map;

									import COM.Example.Main.R;

									import COM.Example.Main.stringGetJson.User;

									import android.app.Activity;

									import android.app.ListActivity;

									import android.os.AsyncTask;

									import android.os.Bundle;

									import android.view.Gravity;

									import android.view.LayoutInflater;

									import android.view.View;

									import android.view.ViewGroup;

									import android.widget.AbsListView;

									import android.widget.AbsListView.OnScrollListener;

									import android.widget.ArrayAdapter;

									import android.widget.ImageView;

									import android.widget.LinearLayout;

									import android.widget.ListView;

									import android.widget.ProgressBar;

									import android.widget.TextView;

									public class stringListActivity extends ListActivity {

									private MyAdapter mMyAdapter;

									private LinkedList<User> users = null;

									// 当前Activity中的ListView

									ListView listView = null;

									int lastItem = 0;

									LinearLayout loadingLayout = null;

									@Override

									public void onCreate(Bundle savedInstanceState) {

									super.onCreate(savedInstanceState);

									setContentView(R.layout.foodlistactivity);

									listView = getListView();

									setLoadingLayout();

									new readTask().execute(null);

									}

									private final class MyAdapter extends ArrayAdapter<User> {

									public MyAdapter(Activity activity, List<User> newsList) {

									super(activity, 0, newsList);

									}

									private Map<Integer, View> viewMap = new HashMap<Integer, View>();

									@Override

									public View getView(int position, View convertView, ViewGroup parent) {

									ViewHolder holder;

									View rowView = this.viewMap.get(position);

									if (rowView == null) {

									User user = users.get(position);

									LayoutInflater inflater = ((Activity) this.getContext())

									.getLayoutInflater();

									holder = new ViewHolder();

									rowView = inflater

									.inflate(R.layout.foodlistactivity_item, null);

									holder.mNameText = (TextView) rowView

									.findViewById(R.id.foodItemUsername);

									holder.mPhoto = (ImageView) rowView

									.findViewById(R.id.foodItemPic);

									rowView.setTag(holder);

									holder.mNameText.setText(user.Name);

									if (!holder.mPhoto.isDrawingCacheEnabled()) {

									holder.mPhoto.setTag(user.Pic);

									new downImageTask().execute(holder.mPhoto);

									holder.mPhoto.setDrawingCacheEnabled(true);

									}

									viewMap.put(position, rowView);

									} else {

									holder = (ViewHolder) rowView.getTag();

									}

									return rowView;

									}

									public class ViewHolder {

									public TextView mNameText;

									public ImageView mPhoto;

									}

									}

									public void setLoadingLayout() {

									LinearLayout layout = new LinearLayout(this);

									layout.setOrientation(LinearLayout.HORIZONTAL);

									ProgressBar progressBar = new ProgressBar(this); progressBar.setPadding(0, 0, 15, 0); layout.addView(progressBar); TextView textView = new TextView(this); textView.setText("加载中..."); textView.setGravity(Gravity.CENTER_VERTICAL); layout.addView(textView); layout.setGravity(Gravity.CENTER); loadingLayout = new LinearLayout(this); loadingLayout.addView(layout); loadingLayout.setGravity(Gravity.CENTER); } private class scrollListener implements OnScrollListener { @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { // 当listView中没有数据，或者数据超过100条，或者不是10的整数倍（即数据不足）时隐藏“更多”并取消onScroll事件的绑定 if (mMyAdapter.getCount() >= 100 || mMyAdapter.getCount() % 10 > 0 || mMyAdapter.getCount() == 0) { listView.removeFooterView(loadingLayout); listView.setOnScrollListener(null); } lastItem = firstVisibleItem + visibleItemCount - 1;// 这里减一是因为有FootView } @Override public void onScrollStateChanged(AbsListView view, int scrollState) { if (lastItem == mMyAdapter.getCount() && scrollState == OnScrollListener.SCROLL_STATE_IDLE) { // 进行翻页操作 new scrollTask().execute(null); } } } public class readTask extends AsyncTask<Object, Void, Void> { @Override protected Void doInBackground(Object... arg0) { users = new stringGetJson().getJson(); return null; } @Override protected void onPostExecute(Void result) { listView.addFooterView(loadingLayout); mMyAdapter = new MyAdapter(stringListActivity.this, users); setListAdapter(mMyAdapter); listView.setOnScrollListener(new scrollListener()); } } public class scrollTask extends AsyncTask<Object, Void, Void> { @Override protected Void doInBackground(Object... arg0) { for (Iterator iterator = new stringGetJson().getJson() .iterator(); iterator.hasNext();) { User user = (User) iterator.next(); users.add(user); } return null; } @Override protected void onPostExecute(Void result) { mMyAdapter.notifyDataSetChanged(); } } }

Json数据来源（这里的例子中把json字符串直接写在代码中了，实际项目中需要改成从网络读取，例子中已经使用了多线程）：

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									package COM.Example.Main;

									import java.lang.reflect.Type;

									import java.util.Iterator;

									import java.util.LinkedList;

									import android.database.MatrixCursor;

									import android.widget.ListView;

									import android.widget.TextView;

									import com.google.gson.Gson;

									import com.google.gson.reflect.TypeToken;

									public class stringGetJson {

									// 设置临时ID，在项目中将被现实的id取代

									private int id = 0;

									public stringGetJson() {

									super();

									}

									//通过getJson方法从Json字符串获取User的列表

									public LinkedList<User> getJson() {

									String jsonData = "[{\"Name\":\"xinuxForJson1\",\"Pic\":\"http://www.qqjay.com/uploads/110414/1_234626_5.jpg\"},{\"Name\":\"xinuxForJson2\",\"Pic\":\"http://www.qqjay.com/uploads/110414/1_234626_3.jpg\"},{\"Name\":\"xinuxForJson3\",\"Pic\":\"http://www.qqjay.com/uploads/110414/1_234626_4.jpg\"},{\"Name\":\"xinuxForJson4\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian1/8.jpg\"},{\"Name\":\"xinuxForJson5\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian1/10.jpg\"},{\"Name\":\"xinuxForJson6\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian1/7.jpg\"},{\"Name\":\"xinuxForJson7\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian1/11.jpg\"},{\"Name\":\"xinuxForJson8\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian1/12.jpg\"},{\"Name\":\"xinuxForJson9\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian1/9.jpg\"},{\"Name\":\"xinuxForJson10\",\"Pic\":\"http://sucai.qqjay.com/fengmian/201104/tupian/7.jpg\"}]";

									Type listType = new TypeToken<LinkedList<User>>() {}.getType();

									Gson gson = new Gson();

									LinkedList<User> users = gson.fromJson(jsonData, listType);

									return users;

									}

									//为getJson提供了数据实体类

									final static class User {

									public String Name;

									public String Pic;

									}

									}

图片下载AsyncTask

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									package COM.Example.Main;

									import COM.Example.FunctionUtility.Download;

									import android.graphics.Bitmap;

									import android.os.AsyncTask;

									import android.widget.ImageView;

									public class downImageTask extends AsyncTask<ImageView, Void, Bitmap> {

									ImageView gView = null;

									@Override

									protected Bitmap doInBackground(ImageView... arg0) {

									gView = (ImageView)arg0[0];

									return Download.getBitmapFromUrl(gView.getTag().toString());

									}

									@Override

									protected void onPostExecute(Bitmap result) {

									if(result != null){

									this.gView.setImageBitmap(result);

									}

									this.gView = null;

									}

									}

网络图片下载类：

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									package COM.Example.FunctionUtility;

									import java.io.BufferedInputStream;

									import java.io.IOException;

									import java.io.InputStream;

									import java.net.MalformedURLException;

									import java.net.URL;

									import android.graphics.Bitmap;

									import android.graphics.BitmapFactory;

									public class Download {

									public static Bitmap getBitmapFromUrl(String imgUrl) {

									URL url;

									Bitmap bitmap = null;

									try {

									url = new URL(imgUrl);

									InputStream is = url.openConnection().getInputStream();

									BufferedInputStream bis = new BufferedInputStream(is);

									bitmap = BitmapFactory.decodeStream(bis);

									bis.close();

									} catch (MalformedURLException e) {

									e.printStackTrace();

									} catch (IOException e) {

									e.printStackTrace();

									}

									return bitmap;

									}

									}