使用AsyncTask异步任务更新进度
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin" >
<Button
android:id="@+id/btn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="start"
android:text="开始" />
<ImageView
android:id="@+id/iv"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
本次demo是展示如何使用AsyncTask更新imageView图片，并练习如何自定义dialog控件实现loading，其中（1）、（2）使用系统的自带dialog控件，（3）为自定义控件
demo使用的布局为：
（1）带圈圈的进度条（使用系统自带控件）
package com.example.asyncdemo;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
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.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
/**
* TODO (这里描述这个类的作用 )
*
* @date: 2013-11-30 下午11:52:32
* @author Hugo
* @version 1.0.0
*/
public class AsyncTaskDemo extends Activity {
private ImageView ivImage;
private static String image_path = "http://ww4.sinaimg.cn/bmiddle/786013a5jw1e7akotp4bcj20c80i3aao.jpg";
private ProgressDialog dialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.async_task);
ivImage = (ImageView) findViewById(R.id.iv);
dialog = new ProgressDialog(this);
dialog.setTitle("提示信息");
dialog.setMessage("正在下载，请稍后...");
dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
}
public void start(View view) {
AsyncTask<String, Void, Bitmap> task = new DownloadImgTask();
task.execute(image_path);
}
private class DownloadImgTask extends AsyncTask<String, Void, Bitmap> {
private Bitmap bitmap;
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog.show();
}
@Override
protected void onProgressUpdate(Void... values) {
// TODO Auto-generated method stub
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(Bitmap result) {
super.onPostExecute(result);
if (null != result) {
ivImage.setImageBitmap(result);
}
dialog.dismiss();
}
@Override
protected Bitmap doInBackground(String... params) {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(params[0]);
bitmap = null;
try {
HttpResponse resp = httpClient.execute(httpGet);
if (HttpStatus.SC_OK == resp.getStatusLine().getStatusCode()) {
HttpEntity entity = resp.getEntity();
Log.i("输入长度", "" + entity.getContentLength());
byte[] bytes = EntityUtils.toByteArray(entity);
Log.i("输出长度", "" + bytes.length);
bitmap = BitmapFactory.decodeByteArray(bytes, 0,
bytes.length);
}
} catch (Exception e) {
e.printStackTrace();
}
return bitmap;
}
}
}
效果如下：
（2）带进度条
package com.example.asyncdemo;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
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.view.View;
import android.widget.ImageView;
/**
* 有进度条的demo
*
* @date: 2013-11-30 下午11:52:32
* @author Hugo
* @version 1.0.0
*/
public class AsyncTaskDemo1 extends Activity {
private ImageView ivImage;
private static String image_path = "http://ww4.sinaimg.cn/bmiddle/786013a5jw1e7akotp4bcj20c80i3aao.jpg";
private ProgressDialog dialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.async_task);
ivImage = (ImageView) findViewById(R.id.iv);
dialog = new ProgressDialog(this);
dialog.setTitle("提示信息");
dialog.setCancelable(false);
dialog.setMessage("正在下载，请稍后...");
dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
}
public void start(View view) {
AsyncTask<String, Integer, Bitmap> task = new DownloadImgTask();
task.execute(image_path);
}
private class DownloadImgTask extends AsyncTask<String, Integer, Bitmap> {
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
dialog.setProgress(values[0]);
}
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog.show();
}
@Override
protected void onPostExecute(Bitmap result) {
super.onPostExecute(result);
if (null != result) {
ivImage.setImageBitmap(result);
}
dialog.dismiss();
}
@Override
protected Bitmap doInBackground(String... params) {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(params[0]);
Bitmap bitmap = null;
InputStream is = null;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
HttpResponse response = httpClient.execute(httpGet);
if (HttpStatus.SC_OK == response.getStatusLine()
.getStatusCode()) {
// 获取输入流
is = response.getEntity().getContent();
// 得到长度
long length = response.getEntity().getContentLength();
byte[] buffer = new byte[1024];
int readLength = 0;
long total = 0;
// 读入数据到缓存
while ((readLength = is.read(buffer)) != -1) {
total += readLength;
// 把缓存中的数据写入输出流
baos.write(buffer, 0, readLength);
// 更新进度
publishProgress((int) (total * 100 / length));
}
// 解码成bitmap
byte[] data = baos.toByteArray();
bitmap = BitmapFactory
.decodeByteArray(data, 0, data.length);
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (null != is) {
is.close();
is = null;
}
if (null != baos) {
baos.close();
baos = null;
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return bitmap;
}
}
}
效果图
