android AsyncTask使用

package com.example.asynctaskdemo;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.nfc.Tag;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

/**
 * 显示一张网络图片
 * 
 * @author crazyandcoder
 * @date [2015-8-9 下午4:11:27]
 */
public class ImageTest extends Activity {

	private String TAG = "ImageTest.class";
	private ImageView mImageView;
	private ProgressBar mProgressBar;
	private TextView mTextProgress;

	private MyAsyncTaskShowImg mTask;
	private static String mImgUrl = "http://h.hiphotos.baidu.com/image/pic/item/9922720e0cf3d7ca14dcc750f71fbe096b63a9ea.jpg";

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		setContentView(R.layout.image);
		initView();

		mTask = new MyAsyncTaskShowImg();
		mTask.execute(mImgUrl);
	}

	private void initView() {
		mTextProgress = (TextView) findViewById(R.id.mTextprogress);
		mImageView = (ImageView) findViewById(R.id.imageView1);
		mProgressBar = (ProgressBar) findViewById(R.id.progress);

	}

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

		/**
		 * 初始化UI控件
		 * 
		 * @see android.os.AsyncTask#onPreExecute()
		 */
		@Override
		protected void onPreExecute() {
			super.onPreExecute();
			mProgressBar.setVisibility(View.VISIBLE);
			mTextProgress.setText("0%");
		}

		/**
		 * 运行复杂的耗时任务
		 * 
		 * @param params
		 * @return
		 * @see android.os.AsyncTask#doInBackground(Params[])
		 */
		@Override
		protected Bitmap doInBackground(String... params) {

			// 网络中图片的地址
			String mImgUrl = params[0];

			String mFileName = "temp_pic";
			Log.d(TAG, "mImgUrl  is " + mImgUrl);
			// 网络中图片终于将转化为bitmap类型返回给imageview显示
			Bitmap mBitmap = null;

			// 获取数据的输入流
			InputStream is = null;
			OutputStream out = null;
			HttpURLConnection connection;

			try {

				// 将网络图片地址以流的方式转化为bitmap类型
				connection = (HttpURLConnection) new URL(mImgUrl).openConnection();
				connection.setDoInput(true);
				connection.setDoOutput(false);

				// 设置链接超时时间
				connection.setConnectTimeout(10 * 1000);
				is = connection.getInputStream();
				out = openFileOutput(mFileName, MODE_PRIVATE);
				byte[] data = new byte[1024];
				// 每次读到的长度
				int seg = 0;
				// 总得数据大小
				long totalSize = connection.getContentLength();
				Log.d(TAG, "total size is " + totalSize);
				// 如今的进度
				long current = 0;
				//
				while (!(mTask.isCancelled()) && (seg = is.read(data)) != -1) {
					// 当前总的进度
					current += seg;
					Log.d(TAG, "current size is " + current);
					// 下载百分比
					int progress = (int) ((float) current / totalSize * 100);

					Log.d(TAG, "progress size is " + progress);
					// 通知更新进度
					publishProgress(progress);
					out.write(data, 0, seg);
				}

				mBitmap = BitmapFactory.decodeFile(getFileStreamPath(mFileName).getAbsolutePath());
				Log.d(TAG, "file is " + getFileStreamPath(mFileName).getAbsolutePath());
				connection.disconnect();
				is.close();
				out.close();

			} catch (MalformedURLException e) {
				e.printStackTrace();

			} catch (IOException e) {
				e.printStackTrace();

			}

			return mBitmap;
		}

		/**
		 * 显示从网络中载入图片的进度
		 * 
		 * @param values
		 * @see android.os.AsyncTask#onProgressUpdate(Progress[])
		 */
		@Override
		protected void onProgressUpdate(Integer... values) {
			super.onProgressUpdate(values);
			mTextProgress.setText(values[0] + "%");
		}

		/**
		 * 将doInBackground中运行的结果返回给该方法，用于更新UI控件
		 * 
		 * @param result
		 * @see android.os.AsyncTask#onPostExecute(java.lang.Object)
		 */
		@Override
		protected void onPostExecute(Bitmap result) {
			super.onPostExecute(result);
			mProgressBar.setVisibility(View.GONE);
			 mTextProgress.setVisibility(View.GONE);
			mImageView.setImageBitmap(result);
			Toast.makeText(ImageTest.this, "图片载入完毕.", Toast.LENGTH_LONG).show();

		}
	}

	@Override
	protected void onPause() {
		super.onPause();
		if (mTask != null && mTask.getStatus() == AsyncTask.Status.RUNNING) {
			//cancel方法仅仅是将AsyncTask相应的状态标记为cancel状态，不是真的取消
			mTask.cancel(true);
		}
	}

}

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