摘要：注意每次需一個(gè)實(shí)例新建的任務(wù)只能執(zhí)行一次否則會(huì)出現(xiàn)異常取消一個(gè)正在執(zhí)行的任務(wù)方法將會(huì)被調(diào)用方法用于在執(zhí)行后臺(tái)任務(wù)前做一些操作方法內(nèi)部執(zhí)行后臺(tái)任務(wù)不可在此方法內(nèi)修改調(diào)用公布進(jìn)度最后方法將被執(zhí)行為了演示進(jìn)度休眠毫秒方法用于更新進(jìn)度信息方法用

private MyTask mTask;  
  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
  
        execute = (Button) findViewById(R.id.execute);  
        execute.setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                //注意每次需new一個(gè)實(shí)例,新建的任務(wù)只能執(zhí)行一次,否則會(huì)出現(xiàn)異常  
                mTask = new MyTask();  
                mTask.execute("http://www.baidu.com");  
  
                execute.setEnabled(false);  
                cancel.setEnabled(true);  
            }  
        });  
        cancel = (Button) findViewById(R.id.cancel);  
        cancel.setOnClickListener(new View.OnClickListener() {  
            @Override  
            public void onClick(View v) {  
                //取消一個(gè)正在執(zhí)行的任務(wù),onCancelled方法將會(huì)被調(diào)用  
                mTask.cancel(true);  
            }  
        });  
        progressBar = (ProgressBar) findViewById(R.id.progress_bar);  
        textView = (TextView) findViewById(R.id.text_view);  
  
    }  
  
    private class MyTask extends AsyncTask {  
        //onPreExecute方法用于在執(zhí)行后臺(tái)任務(wù)前做一些UI操作  
        @Override  
        protected void onPreExecute() {  
            Log.i(TAG, "onPreExecute() called");  
            textView.setText("loading...");  
        }  
  
        //doInBackground方法內(nèi)部執(zhí)行后臺(tái)任務(wù),不可在此方法內(nèi)修改UI  
        @Override  
        protected String doInBackground(String... params) {  
            Log.i(TAG, "doInBackground(Params... params) called");  
            try {  
                HttpClient client = new DefaultHttpClient();  
                HttpGet get = new HttpGet(params[0]);  
                HttpResponse response = client.execute(get);  
                if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {  
                    HttpEntity entity = response.getEntity();  
                    InputStream is = entity.getContent();  
                    long total = entity.getContentLength();  
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();  
                    byte[] buf = new byte[1024];  
                    int count = 0;  
                    int length = -1;  
                    while ((length = is.read(buf)) != -1) {  
                        baos.write(buf, 0, length);  
                        count += length;  
                        //調(diào)用publishProgress公布進(jìn)度,最后onProgressUpdate方法將被執(zhí)行  
                        publishProgress((int) ((count / (float) total) * 100));  
                        //為了演示進(jìn)度,休眠500毫秒  
                        Thread.sleep(500);  
                    }  
                    return new String(baos.toByteArray(), "gb2312");  
                }  
            } catch (Exception e) {  
                Log.e(TAG, e.getMessage());  
            }  
            return null;  
        }  
  
        //onProgressUpdate方法用于更新進(jìn)度信息  
        @Override  
        protected void onProgressUpdate(Integer... progresses) {  
            Log.i(TAG, "onProgressUpdate(Progress... progresses) called");  
            progressBar.setProgress(progresses[0]);  
            textView.setText("loading..." + progresses[0] + "%");  
        }  
  
        //onPostExecute方法用于在執(zhí)行完后臺(tái)任務(wù)后更新UI,顯示結(jié)果  
        @Override  
        protected void onPostExecute(String result) {  
            Log.i(TAG, "onPostExecute(Result result) called");  
            textView.setText(result);  
  
            execute.setEnabled(true);  
            cancel.setEnabled(false);  
        }  
  
        //onCancelled方法用于在取消執(zhí)行中的任務(wù)時(shí)更改UI  
        @Override  
        protected void onCancelled() {  
            Log.i(TAG, "onCancelled() called");  
            textView.setText("cancelled");  
            progressBar.setProgress(0);  
  
            execute.setEnabled(true);  
            cancel.setEnabled(false);  
        }  
    }  
}