Androidの多线程之更新ui（AsyncTask）

AsyncTask

构造（泛型参数）

外部步骤：

AsyncTask task = new AsyncTask<params,values,result>();

task.exec(params);

内部流程：

1.void onPreExecute() ;//里头可放些提醒类的东西

2.result doInBackground(params){publishProgress(values);};//执行任务，取得结果并返回

3.void onProgressUpdate(values);//接收publishProgress()参数,可以更新进度

4.void onPostExecute(result);//执行完成，取得结果，可在UI上展示

package com.bvin.aync;

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 android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class AyncActivity extends Activity {
    /** Called when the activity is first created. */
    private ImageView iv;
    private ProgressDialog dialog;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       
        initViews();
    }
    
    private void initViews(){
        Button bt = (Button)findViewById(R.id.bt);
        iv =  (ImageView)findViewById(R.id.iv);
        
        bt.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                loadImages();
            }
        });
        
        dialog = new ProgressDialog(this);
        
    }
    
    private void loadImages(){
        
        LoadImageTask task = new LoadImageTask();
        task.execute("http://avatar.csdn.net/0/3/4/1_mylzc.jpg");
    }
    
    class LoadImageTask extends AsyncTask<String,Integer,Bitmap>{

        @Override
        protected Bitmap doInBackground(String... params) {
            // TODO Auto-generated method stub
            Bitmap bitmap  = null;
            HttpGet get = new HttpGet(params[0]);
            HttpClient client = new DefaultHttpClient();
            try {
                HttpResponse res = client.execute(get);
                bitmap = BitmapFactory.decodeStream(res.getEntity().getContent());
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
            
            return bitmap;
        }

        @Override
        protected void onPostExecute(Bitmap result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            dialog.dismiss();
            if(result!=null){
                iv.setImageBitmap(result);
                Toast.makeText(AyncActivity.this, "图片下载成功", 1000).show();
                
            }else{
                
                Toast.makeText(AyncActivity.this, "图片下载失败", 1000).show();
            }
            
        }

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
            dialog.show();
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            // TODO Auto-generated method stub
            super.onProgressUpdate(values);
        }

        
        
        
        
    }
}