Android中使用Handler實現(xiàn)下載網(wǎng)絡(luò)圖片應(yīng)用的代碼清單

1、Android中使用Handler實現(xiàn)下載網(wǎng)絡(luò)圖片應(yīng)用的代碼清單范美英（北京信息職業(yè)技術(shù)學院）摘 要：Android應(yīng)用開發(fā)中可以使用Handler處理消息，本文詳細羅列了使用Handler從網(wǎng)絡(luò)下載圖片的代碼清單。關(guān)鍵詞： Android；Handler；代碼清單1 src/MainActivity.java類的代碼方案1：package com.zyk.download_pics;import org.apache.http.HttpResponse;import org.apache.http.client.HttpClient;import org.apache.http.client

2、.methods.HttpGet;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.util.EntityUtils;import android.app.Activity;import android.app.ProgressDialog;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Bundle;import android.os.Handler;import a

3、ndroid.os.Message;import android.view.View;import android.widget.Button;import android.widget.ImageView;import android.widget.Toast;public class MainActivity extends Activity ImageView img_pics;Button btn_download;private static Bitmap bitmap=null;private String imgPath = "private static final

4、int DOWNLOAD_IMG = 1; private ProgressDialog dialog = null; private Handler handler = new Handler() /處理子線程發(fā)送的消息Override public void handleMessage(Message msg) byte data = (byte)msg.obj; bitmap = BitmapFactory.decodeByteArray(data, 0, data.length); img_pics.setImageBitmap(bitmap); if(msg.what = DOWNL

5、OAD_IMG) dialog.dismiss(); ; ; Overrideprotected void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);img_pics=(ImageView) this.findViewById(R.id.img_down_pics);btn_download=(Button) this.findViewById(R.id.btn_download);dialog = new Progr

6、essDialog(this); dialog.setTitle("提示"); dialog.setMessage("正在下載，請稍后."); dialog.setCancelable(false); public void clickDownload(View v)new Thread(new MyThread().start(); dialog.show(); public class MyThread implements Runnable / 在run方法中完成網(wǎng)絡(luò)耗時的操作 Override public void run() HttpClie

7、nt httpClient = new DefaultHttpClient(); HttpGet httpGet = new HttpGet(imgPath); HttpResponse httpResponse = null; try httpResponse = httpClient.execute(httpGet); if(200 = httpResponse.getStatusLine().getStatusCode() byte data = EntityUtils.toByteArray(httpResponse.getEntity();/ 這里的數(shù)據(jù)data我們必須發(fā)送給UI的主

8、線程，所以我們通過Message的方式來做橋梁。 Message message = Message.obtain(); message.obj = data; message.what = DOWNLOAD_IMG; handler.sendMessage(message); catch (Exception e) Toast.makeText(MainActivity.this, e.toString(), Toast.LENGTH_LONG).show(); Overrideprotected void onDestroy() if(bitmap!=null)bitmap.recycle

9、();super.onDestroy(); 方案2：package com.zyk.download_pics;import java.io.InputStream;import .HttpURLConnection;import .URL;import android.app.Activity;import android.app.ProgressDialog;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Bundle;import android.os.Handl

10、er;import android.os.Message;import android.view.View;import android.widget.Button;import android.widget.ImageView;import android.widget.Toast;public class MainActivity extends Activity ImageView img_pics;Button btn_download;private static Bitmap bitmap=null;private String imgPath = "private st

11、atic final int DOWNLOAD_IMG = 1; private ProgressDialog dialog = null; private Handler handler = new Handler() / 處理子線程給我們發(fā)送的消息。 Override public void handleMessage(android.os.Message msg) img_pics.setImageBitmap(bitmap); if(msg.what = DOWNLOAD_IMG) dialog.dismiss(); ; ; Overrideprotected void onCreat

12、e(Bundle savedInstanceState) super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);img_pics=(ImageView) this.findViewById(R.id.img_down_pics);btn_download=(Button) this.findViewById(R.id.btn_download);dialog = new ProgressDialog(this); dialog.setTitle("提示"); dialog.setM

13、essage("正在下載，請稍后."); dialog.setCancelable(false); public void clickDownload(View v)new Thread(new MyThread().start(); dialog.show(); public class MyThread implements Runnable / 在run方法中完成網(wǎng)絡(luò)耗時的操作 Override public void run() try URL url = new URL(imgPath);HttpURLConnection conn = (HttpURLConne

14、ction)url.openConnection();InputStream inputStream=conn.getInputStream();bitmap = BitmapFactory.decodeStream(inputStream); / 必須將數(shù)據(jù)發(fā)送給UI的主線程，通過Message的方式來做橋梁。 Message message = Message.obtain(); message.what = DOWNLOAD_IMG; handler.sendMessage(message); catch (Exception e) Toast.makeText(MainActivity

15、_another.this, e.toString(), Toast.LENGTH_LONG).show(); Overrideprotected void onDestroy() if(bitmap!=null)bitmap.recycle();super.onDestroy(); 2 res/layout/activity_main.xml的代碼清單<LinearLayout xmlns:android=" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <Button android:id="+id/btn_download" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="開始下載" android:onClick="