AsyncTask的用法

package test.list;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.util.ArrayList;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
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.content.Context;
import android.content.DialogInterface;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

publicclass NetworkActivity extends Activity{
private TextView message;
private Button open;
private EditText url;

@Override
publicvoid onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.network);
message= (TextView) findViewById(R.id.message);
url= (EditText) findViewById(R.id.url);
open= (Button) findViewById(R.id.open);
open.setOnClickListener(new View.OnClickListener() {
publicvoid onClick(View arg0) {
connect();
}
});

}

privatevoid connect() {
PageTask task =new PageTask(this);
task.execute(url.getText().toString());
}


class PageTask extends AsyncTask<String, Integer, String> {
// 可变长的输入参数，与AsyncTask.exucute()对应
ProgressDialog pdialog;
public PageTask(Context context){
pdialog =new ProgressDialog(context, 0);
pdialog.setButton("cancel", new DialogInterface.OnClickListener() {
publicvoid onClick(DialogInterface dialog, int i) {
dialog.cancel();
}
});
pdialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
publicvoid onCancel(DialogInterface dialog) {
finish();
}
});
pdialog.setCancelable(true);
pdialog.setMax(100);
pdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pdialog.show();


}
@Override
protected String doInBackground(String... params) {

try{

HttpClient client =new DefaultHttpClient();
// params[0]代表连接的url
HttpGet get =new HttpGet(params[0]);
HttpResponse response = client.execute(get);
HttpEntity entity = response.getEntity();
long length = entity.getContentLength();
InputStream is = entity.getContent();
String s =null;
if(is !=null) {
ByteArrayOutputStream baos =new ByteArrayOutputStream();

byte[] buf =newbyte[128];

int ch =-1;

int count =0;

while((ch = is.read(buf)) !=-1) {

baos.write(buf, 0, ch);

count += ch;

if(length >0) {
// 如果知道响应的长度，调用publishProgress（）更新进度
publishProgress((int) ((count / (float) length) *100));
}

// 让线程休眠100ms
Thread.sleep(100);
}
s =new String(baos.toByteArray()); }
// 返回结果
return s;
} catch(Exception e) {
e.printStackTrace();

}

returnnull;

}

@Override
protectedvoid onCancelled() {
super.onCancelled();
}

@Override
protectedvoid onPostExecute(String result) {
// 返回HTML页面的内容
message.setText(result);
pdialog.dismiss();
}

@Override
protectedvoid onPreExecute() {
// 任务启动，可以在这里显示一个对话框，这里简单处理
message.setText(R.string.task_started);
}

@Override
protectedvoid onProgressUpdate(Integer... values) {
// 更新进度
System.out.println(""+values[0]);
message.setText(""+values[0]);
pdialog.setProgress(values[0]);
}

}

}