AsyncTask异步交互的用法简介

<span style="font-size:18px;">/**
* @author WJL <span style="color:#ff0000;">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</span>
*/
public class MyAsyncTask extends AsyncTask<String, Double, String> {
TextView textView;
ProgressBar bar;
/**
* @param textView
* @param bar
*/
public MyAsyncTask(TextView textView, ProgressBar bar) {
this.textView=textView;
this.bar=bar;
}

// Runs on the UI thread before doInBackground.
@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
<span style="color:#ff0000;">protected String doInBackground(String... params)</span> {

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;

}

// Runs on the UI thread after doInBackground.
// 运行在主线程,在doInBackground方法之后执行,接收doInBackground方法的返回值</span>

<span style="font-size:18px;">在此方法内更新UI线程中的控件
<span style="color:#ff0000;">protected void onPostExecute(String result)</span> {

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();*/

////////////////////////////////////////////////

}

}</span>

<span style="font-size:18px;">public class MainActivity extends Activity {
//	String path="http://169.254.214.171:8080/bwie/city.json";
String key = "3ac9f31ff66b9746539472887b3799c3";
// 通过get请求时的接口地址
String get_path = "http://web.juhe.cn:8080/constellation/getAll?consName=狮子座&type=today&key="
+ key;
private TextView textView;
private ProgressBar bar;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = (TextView) findViewById(R.id.textView);
ProgressBar	bar = (ProgressBar) findViewById(R.id.pro);
MyAsyncTask myAsyncTask=new MyAsyncTask(textView,bar);
try {

String string = myAsyncTask.execute(get_path).get();
textView.setText(string);
System.out.println(string);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}</span>