Android 中使用 AsyncTask 非同步讀取網狀圖片_Android

 1.建立Android工程AsyncLoadPicture

建立布局檔案activity_main.xml主介面為一個GridView，還有其子項布局檔案gridview_item.xml

2.功能主介面MainActivity.java,主代碼如下

package com.example.asyncloadpicture;import java.util.ArrayList;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.AsyncTask;import android.os.Bundle;import android.widget.GridView;/*** @author ymw* @data --*/public class MainActivity extends Activity {private GridView gridViewImg;private ArrayList<ImageEntity> imageList = new ArrayList<ImageEntity>();@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);gridViewImg = (GridView) findViewById(R.id.gridViewImg);initData();}private void initData() {for (int i = ; i < ; i++) {ImageEntity b = new ImageEntity();b.setImage(BitmapFactory.decodeResource(getResources(),R.drawable.nopicture));imageList.add(b);}ImageAdapter adapter = new ImageAdapter(getApplicationContext(),imageList);gridViewImg.setAdapter(adapter);String[] params = {"http://images.cnitblog.com/i///.png","p" };new ImageLoadTask(getApplicationContext(), adapter).execute(params);}/** 圖片非同步載入類 */public class ImageLoadTask extends AsyncTask<String, Void, Void> {private ImageAdapter adapter;public ImageLoadTask(Context context, ImageAdapter adapter) {this.adapter = adapter;}@Overrideprotected Void doInBackground(String... params) {String url = params[];// 擷取傳來的參數，圖片uri地址String p = params[];for (int i = ; i < adapter.getCount(); i++) {ImageEntity bean = (ImageEntity) adapter.getItem(i);Bitmap bitmap = BitmapFactory.decodeStream(Request.HandlerData(url));bean.setImage(bitmap);publishProgress(); // 通知去更新UI}return null;}public void onProgressUpdate(Void... voids) {if (isCancelled())return;// 更新UIadapter.notifyDataSetChanged();}}/** 圖片實體 */public class ImageEntity {private Bitmap image;public Bitmap getImage() {return image;}public void setImage(Bitmap image) {this.image = image;}}}

3.GridView列表圖片適配器代碼ImageAdapter.java

package com.example.asyncloadpicture;import java.util.ArrayList;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ImageView;import com.example.asyncloadpicture.MainActivity.ImageEntity;/*** * @author ymw* @data -- 圖片適配器*/public class ImageAdapter extends BaseAdapter {private Context _context;private ArrayList<ImageEntity> _list;public ImageAdapter(Context context, ArrayList<ImageEntity> imageList) {this._context = context;this._list = imageList;}@Overridepublic int getCount() {return _list.size();}@Overridepublic Object getItem(int position) {return _list.get(position);}@Overridepublic long getItemId(int position) {return position;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {LayoutInflater inflater = LayoutInflater.from(_context);convertView = inflater.inflate(R.layout.gridview_item, null);ImageView imgView = (ImageView) convertView.findViewById(R.id.imgView);ImageEntity b = _list.get(position);// 如果有圖片則讀取，沒有則跳過if (b.getImage() != null) {imgView.setImageBitmap(b.getImage());}return convertView;}}

4.請求網路讀取圖片的類Request.java

package com.example.asyncloadpicture;import java.io.IOException;import java.io.InputStream;import java.net.URL;import java.net.URLConnection;import android.graphics.drawable.Drawable;import android.util.Log;/*** 工具類，主要根據url讀取圖片返迴流的方法* * @author ymw* */public class Request {public static InputStream HandlerData(String url) {InputStream inStream = null;try {URL feedUrl = new URL(url);URLConnection conn = feedUrl.openConnection();conn.setConnectTimeout( * );inStream = conn.getInputStream();} catch (Exception e) {e.printStackTrace();}return inStream;}/** 直接返回Drawable對象設定圖片 */public static Drawable loadImageFromNetwork(String imageUrl) {Drawable drawable = null;try {// 可以在這裡通過檔案名稱來判斷，是否本地有此圖片drawable = Drawable.createFromStream(new URL(imageUrl).openStream(), "image.jpg");} catch (IOException e) {Log.d("test", e.getMessage());}if (drawable == null) {Log.d("test", "null drawable");} else {Log.d("test", "not null drawable");}return drawable;}}

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