AsyncTask 和 Handler

一、AsyncTask和Handler的初步了解

    1.AsyncTask的初识

         介绍：http://blog.sina.com.cn/s/blog_8417aea80100t6y2.html

         使用实例：http://blog.youkuaiyun.com/qianfu111/article/details/10200105

            附上使用实例中的代码

             MainActivity：

               

package com.example.mygeneralutil;

import java.net.URI;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.Toast;

public class MainActivity extends Activity {

	private Button mDownloadBtn;
	private Button mCancelBtn;
	private ImageView mImage1;
	private ImageView mImage2;
	private ProgressBar mProgress1;
	private ProgressBar mProgress2;
	private GetLogoFromInternet mTask;
	private String TAG = "GetLogoFromInternet";

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.asynctask_activity);
		initComponent();
	}

	private void initComponent() {

		mDownloadBtn = (Button) findViewById(R.id.button1);
		mDownloadBtn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				mTask = new GetLogoFromInternet();
				mTask.execute(
						"http://d.hiphotos.baidu.com/album/w%3D2048/sign=6b4e0cbb023b5bb5bed727fe02ebd439/7dd98d1001e939016245802e7aec54e736d1965e.jpg",
						"http://a.hiphotos.baidu.com/album/w%3D2048/sign=4a44fc70342ac65c67056173cfcab311/b8389b504fc2d562f5f6f0fde61190ef76c66c27.jpg");

			}
		});
		mCancelBtn = (Button) findViewById(R.id.button2);
		mCancelBtn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				mTask.cancel(true);
			}
		});

		mImage1 = (ImageView) findViewById(R.id.imageView1);
		mImage2 = (ImageView) findViewById(R.id.imageView2);
		mProgress1 = (ProgressBar) findViewById(R.id.progressBar1);
		mProgress2 = (ProgressBar) findViewById(R.id.progressBar2);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	class GetLogoFromInternet extends AsyncTask<String, Integer, Bitmap> {

		private Bitmap bitmap = null;

		@Override
		protected void onPreExecute() {
			mImage1.setImageBitmap(null);
			mImage2.setImageBitmap(null);
			mProgress1.setProgress(0);
			mProgress2.setProgress(0);
			Log.e(TAG, "onPreExecute");
		}

		@Override
		protected Bitmap doInBackground(String... params) {
			publishProgress(0, 0);

			HttpClient hc = new DefaultHttpClient();
			publishProgress(30, 0);
			HttpGet hg = new HttpGet();
			Bitmap bitmap2 = null;
			try {
				hg.setURI(new URI(params[0]));
				HttpResponse response = hc.execute(hg);
				bitmap = BitmapFactory.decodeStream(response.getEntity()
						.getContent());
				publishProgress(100, 30);

				hg.setURI(new URI(params[1]));
				HttpResponse response2 = hc.execute(hg);
				bitmap2 = BitmapFactory.decodeStream(response2.getEntity()
						.getContent());

			} catch (Exception e) {
				Log.e(TAG, "" + e.getMessage());
			}
			publishProgress(100, 100);
			Log.e(TAG, "doInBackground");
			// mImage1.setImageBitmap(bitmap);//error
			return bitmap2;

		}

		@Override
		protected void onProgressUpdate(Integer... values) {
			mProgress1.setProgress(values[0]);
			mProgress2.setProgress(values[1]);
			Log.e(TAG, "onProgressUpdate");
		}

		@Override
		protected void onPostExecute(Bitmap result) {
			if (result != null) {
				mImage1.setImageBitmap(bitmap);
				mImage2.setImageBitmap(result);
				Toast.makeText(MainActivity.this,
						"get image from network successful", Toast.LENGTH_SHORT)
						.show();
			} else {
				Toast.makeText(MainActivity.this,
						"get image from network error", Toast.LENGTH_SHORT)
						.show();
			}
			Log.e(TAG, "onPostExecute");
		}

		@Override
		protected void onCancelled() {
			mProgress1.setProgress(0);
			mProgress2.setProgress(0);
			Log.e(TAG, "onCancelled");
		}

	}
}

    

         布局文件：

          

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ffffff"
    android:orientation="vertical" >

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="10dp" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:orientation="vertical" >

            <ProgressBar
                android:id="@+id/progressBar1"
                style="?android:attr/progressBarStyleHorizontal"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />

            <ImageView
                android:id="@+id/imageView1"
                android:layout_width="150dp"
                android:layout_height="150dp" />

            <ProgressBar
                android:id="@+id/progressBar2"
                style="?android:attr/progressBarStyleHorizontal"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />

            <ImageView
                android:id="@+id/imageView2"
                android:layout_width="150dp"
                android:layout_height="150dp" />

            <Button
                android:id="@+id/button1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="download image" />

            <Button
                android:id="@+id/button2"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="cancel download image" />
        </LinearLayout>
    </ScrollView>

</LinearLayout>

    2.Handler的初识

      介绍：主要接受子线程发送的数据, 并用此数据配合主线程更新UI. 

     用法：之前曾使用过

 

二、AsyncTask 和 Handler的异同点

     http://blog.sina.com.cn/s/blog_8417aea80100t6y2.html

     http://blog.youkuaiyun.com/onlyonecoder/article/details/8484200