AsyncTask的用法小例子

/**
 * 第一个泛型:规定doInBackground方法的参数类型,规定AsyncTask.execute方法传递的参数类型
 *         第二个泛型:规定onProgressUpdate方法参数的类型,publishProgress参数类型
 *         第三个泛型:规定doInBackground方法的返回值类型
 */
public class MyAsyncTask extends AsyncTask<String, Double, String> {
TextView textView;
ProgressBar bar;
public MyAsyncTask(TextView textView, ProgressBar bar) {
this.textView=textView;
this.bar=bar;
}


@Override
// 运行在主线程,在doInBackground方法之前执行
protected void onPreExecute() {
System.out.println("准备联网");
}


@Override
// 运行在子线程,做耗时操作
// 返回值被onPostExecute接收
protected String doInBackground(String... params) {


String string = "100";


HttpClient httpClient = new DefaultHttpClient();


// 做联网请求,得到传递的参数,因为是可变长度的数组,想取第一个参数,所以去角


标为0的元素
HttpGet httpGet = new HttpGet(params[0]);


try {


HttpResponse httpResponse = httpClient.execute(httpGet);


if (httpResponse.getStatusLine().getStatusCode() == 200) {


HttpEntity httpEntity = httpResponse.getEntity();
//得到实体里的json
string = EntityUtils.toString(httpEntity);

}


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


return string;


}


// 运行在主线程,在doInBackground方法之后执行,接收doInBackground方法的返回值
protected void onPostExecute(String result) {


System.out.println(result);
//更新进度
// publishProgress(100d);
};




// 更新进度,运行在主线程上,在publishProgress运行之后
protected void onProgressUpdate(Double[] values) {
// System.out.println("执行进度:" + values[0]);
double r = values[0];
//向上取整
double floor = Math.ceil(r );

textView.setText(floor+"");
// bar.setProgress(double.);
};



//获取进度
public void progress(){

/* // 获取数据总长度
long contentLength = httpEntity.getContentLength();
System.out.println(contentLength);
// 获取网络数据
InputStream inputStream = httpEntity.getContent();


BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(inputStream, "utf-8"));


char[] buf = new char[1];
        //总读取进度
int sun = 0;
//本次读取的进度
        int i;
        StringBuilder buffer=new StringBuilder();
while ((i = bufferedReader.read(buf)) != -1) {

sun=sun+i;
double count = (((double)sun / (double)contentLength))*100;

             //实时更新进度
publishProgress(count); 
buffer.append(new String(buf));
}


bufferedReader.close();
inputStream.close();
       string = buffer.toString()


////////////////////////////////////////////////;*/

}

}