异步任务AsyncTask进阶

现在开始一个示例使用AsyncTask加载网络图片：

1. 首先布局文件：用ProgressBar来起到缓冲效果，在图片未加载完毕之前显示ProgressBar

2. MainActivity.java代码：

public class MainActivity extends Activity {

private ImageView mImageView;

private ProgressBar mProgressBar;

private static String URL ="http://img3.imgtn.bdimg.com/it/u=3960315235,1990804806&fm=11&gp=0.jpg";

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

mImageView = (ImageView) findViewById(R.id.iv);

mProgressBar = (ProgressBar) findViewById(R.id.pb);

// 设置传递进去的参数

new MyAsyncTask().execute(URL);

}

class MyAsyncTask extends AsyncTask {

@Override

protected void onPreExecute() {

super.onPreExecute();

mProgressBar.setVisibility(View.VISIBLE);

}

@Override

protected void onPostExecute(Bitmap bitmap) {

super.onPostExecute(bitmap);

mProgressBar.setVisibility(View.INVISIBLE);

mImageView.setImageBitmap(bitmap);

}

@Override

protected Bitmap doInBackground(String... params) {

// 获取传进来的参数

String url = params[0];

Bitmap bitmap = null;

URLConnection conn = null;

InputStream is = null;

BufferedInputStream bis = null;

try {

conn = new URL(url).openConnection();

is = conn.getInputStream();

bis = new BufferedInputStream(is);

// 通过decodeStream来解析输入流

bitmap = BitmapFactory.decodeStream(bis);

} catch (IOException e) {

e.printStackTrace();

} finally {

try {

if (is != null) {

is.close();

}

} catch (IOException e) {

e.printStackTrace();

}

try {

if (bis != null) {

bis.close();

}

} catch (IOException e) {

e.printStackTrace();

}

}

return bitmap;

}

}

}

3. 由于涉及到了网络请求，记住最后在manifast.xml文件中添加网络权限：

4.结果：在请求到图片结果之前是显示一个ProgressBar转圈圈的，之后显示一张图片，我用的一种图片地址是我女神一张网络图片地址，哈哈，看到女神的图片很是开心呐！学习编程真是一件神奇的事情呢！