异步任务（AsyncTask）

  1 public class MainActivity extends AppCompatActivity {
  2 
  3  
  4 
  5     private TextView show;
  6 
  7  
  8 
  9     @Override
 10 
 11     protected void onCreate(Bundle savedInstanceState) {
 12 
 13         super.onCreate(savedInstanceState);
 14 
 15         setContentView(R.layout.activity_main);
 16 
 17         show = (TextView) findViewById(R.id.show);
 18 
 19  
 20 
 21     }
 22 
 23  
 24 
 25     public void download(View source) throws MalformedURLException{
 26 
 27         DownTask task = new DownTask(this);
 28 
 29         task.execute(new URL("http://www.crazyit.org/ethos.php"));
 30 
 31     }
 32 
 33  
 34 
 35     private class DownTask extends AsyncTask<URL, Integer, String> {
 36 
 37         ProgressDialog pdialog;
 38 
 39         int hasRead = 0;
 40 
 41         Context mContext;
 42 
 43         public DownTask(Context ctxt){
 44 
 45             mContext = ctxt;
 46 
 47         }
 48 
 49  
 50 
 51         @Override
 52 
 53         protected String doInBackground(URL... params) {
 54 
 55             StringBuilder sb = new StringBuilder();
 56 
 57             try{
 58 
 59             URLConnection conn = params[0].openConnection();
 60 
 61             BufferedReader br = new BufferedReader(
 62 
 63                     new InputStreamReader(conn.getInputStream(),"utf-8"));
 64 
 65             String line = null;
 66 
 67             while ((line = br.readLine()) != null){
 68 
 69                 sb.append(line + "\n");
 70 
 71                 hasRead++;
 72 
 73                 publishProgress(hasRead);
 74 
 75             }
 76 
 77             return sb.toString();
 78 
 79             }
 80 
 81             catch (Exception e){
 82 
 83                 e.printStackTrace();
 84 
 85             }
 86 
 87             return null;
 88 
 89         }
 90 
 91  
 92 
 93         @Override
 94 
 95         protected void onPostExecute(String s) {
 96 
 97             show.setText(s);
 98 
 99             pdialog.dismiss();
100 
101         }
102 
103  
104 
105         @Override
106 
107         protected void onPreExecute() {
108 
109             pdialog = new ProgressDialog(mContext);
110 
111             pdialog.setTitle("任务执行中");
112 
113             pdialog.setMessage("任务正在进行中，敬请等待...");
114 
115             pdialog.setCancelable(false);
116 
117             pdialog.setMax(202);
118 
119             pdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
120 
121             pdialog.setIndeterminate(false);
122 
123             pdialog.show();
124 
125         }
126 
127  
128 
129         @Override
130 
131         protected void onProgressUpdate(Integer... values) {
132 
133             show.setText("已经读取了【" + values[0] + "】行！");
134 
135             pdialog.setProgress(values[0]);
136 
137         }
138 
139     }
140 
141 }