Handler Post下载图片-优快云博客

本文介绍了一个简单的Android应用程序，该程序演示了如何使用多线程从网络URL加载并显示一张图片。通过创建一个带有按钮和图片视图的界面，用户可以触发图片的下载过程，并在下载完成后将图片显示在界面上。

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1. MainActivity代码：

import java.io.IOException;

import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.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 android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class ImageActivity extends Activity {

	private Button myButton = null;
	private ImageView imageView = null;
	private static final String image_path = "http://11.203.18.14:8080/source/001.png";
	private ProgressDialog dialog = null;
	
	private Handler handler = new Handler();
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		myButton = (Button)findViewById(R.id.myButton);
	    imageView = (ImageView)findViewById(R.id.imageView);
	    
	    dialog = new ProgressDialog(ImageActivity.this);
	    dialog.setTitle("提示");
	    dialog.setMessage("正在下载，请稍后......");
	    dialog.setCancelable(false);
	    myButton.setOnClickListener(new View.OnClickListener() {
			
			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				new Thread(new MyThread()).start();
				dialog.show();
			}
		});
	}

	
	public class MyThread implements Runnable {
		
		@Override
		public void run() {
			// TODO Auto-generated method stub
			HttpClient httpClient = new DefaultHttpClient();
			HttpGet httpGet = new HttpGet(image_path);
			HttpResponse httpResponse = null;
			
			try {
				httpResponse = httpClient.execute(httpGet);
				if(httpResponse.getStatusLine().getStatusCode()==200){
					byte[] data = EntityUtils.toByteArray(httpResponse.getEntity());
					final Bitmap bmp = BitmapFactory.decodeByteArray(data, 0, data.length);
					handler.post(new Runnable() {
						
						@Override
						public void run() {
							// TODO Auto-generated method stub
							imageView.setImageBitmap(bmp);
						}
					});
					dialog.dismiss();
				}
			} catch (ClientProtocolException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.image, menu);
		return true;
	}



}

2. main.xml代码

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">
    
    <Button 
        android:id="@+id/myButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="下载"/>
    
    <ImageView 
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"/>
</LinearLayout>

3. 注册网络访问权限

<uses-permission android:name="android.permission.INTERNET"/>