异步加载数据的三种实现

转自：

http://www.2cto.com/kf/201210/159608.html

[java] package com.testasyntextview; /** * 把获取的线程写到方法中(比较好) */ import android.app.Activity; import android.app.ProgressDialog; import android.content.Context; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.text.Html; import android.text.Spanned; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView;  public class MethodTestAsynTextViewActivity extends Activity {     private TextView textView1;     private Button button1;     private Context context;     private ProgressDialog progressDialog;     private Spanned html;      /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);         context = this;         textView1 = (TextView) findViewById(R.id.textView1);         button1 = (Button) findViewById(R.id.button1);         button1.setOnClickListener(l);      }      private OnClickListener l = new OnClickListener() {          @Override         public void onClick(View v) {              progressDialog = ProgressDialog.show(context, "获取数据中", "等待");             getHtmlDate();          }     };      private void getHtmlDate() {// 获取数据,把线程写入了其中         new Thread() {             public void run() {                 Message msg = myHandler.obtainMessage();                 try {                     html = HttpUtil.fromHtml(HttpUtil                             .getHtml("http://wap.sina.com"));                     msg.what = 0;                 } catch (Exception e) {                     e.printStackTrace();                     msg.what = 1;                 }                  myHandler.sendMessage(msg);             }         }.start();     }      Handler myHandler = new Handler() {          public void handleMessage(Message msg) {             switch (msg.what) {             case 0:                 textView1.setText(html);                 progressDialog.dismiss();                 break;             case 1:                 textView1.setText("当前无数据");                 progressDialog.dismiss();                 break;             }             super.handleMessage(msg);         }     };  } [java] package com.testasyntextview;  /** * 使用AsyncTask类 */ import android.app.Activity; import android.app.ProgressDialog; import android.content.Context; import android.os.AsyncTask; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.text.Html; import android.text.Spanned; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView;  public class TestAsynTextViewActivity extends Activity {     private TextView textView1;     private Button button1;     private Context context;     private ProgressDialog progressDialog;     private Spanned html;      /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);         context = this;          progressDialog = new ProgressDialog(context);         progressDialog.setTitle("进度条");         progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);          textView1 = (TextView) findViewById(R.id.textView1);         button1 = (Button) findViewById(R.id.button1);         button1.setOnClickListener(l);      }      private OnClickListener l = new OnClickListener() {          @Override         public void onClick(View v) {             new InitTask().execute("http://wap.sina.com",                     "http://wap.baidu.com");          }     };      private void getHtmlDate(String url) {// 获取数据,把线程写入了其中          try {             html = HttpUtil.fromHtml(HttpUtil.getHtml(url));         } catch (Exception e) {             e.printStackTrace();         }      }      /**     * When an asynchronous task is executed, the task goes through 4 steps:     *      * onPreExecute(),      * invoked on the UI thread immediately after the task is     * executed. This step is normally used to setup the task, for instance by     * showing a progress bar in the user interface.      *      * doInBackground(Params...),     * invoked on the background thread immediately after onPreExecute()     * finishes executing. This step is used to perform background computation     * that can take a long time. The parameters of the asynchronous task are     * passed to this step. The result of the computation must be returned by     * this step and will be passed back to the last step. This step can also     * use      *      * publishProgress(Progress...) to publish one or more units of     * progress. These values are published on the UI thread, in the     *      * onProgressUpdate(Progress...) step. onProgressUpdate(Progress...),     * invoked on the UI thread after a call to publishProgress(Progress...).     * The timing of the execution is undefined. This method is used to display     * any form of progress in the user interface while the background     * computation is still executing. For instance, it can be used to animate a     * progress bar or show logs in a text field. onPostExecute(Result), invoked     * on the UI thread after the background computation finishes. The result of     * the background computation is passed to this step as a parameter.     */      class InitTask extends AsyncTask<String, Integer, Long> {         protected void onPreExecute() {             progressDialog.show();             super.onPreExecute();          }          protected Long doInBackground(String... params) {// Long是结果 String 是入口参数              getHtmlDate(params[0]);// 可以运行两个任务             publishProgress(50);// 发送进度50%             getHtmlDate(params[1]);             publishProgress(100);// 发送进度100%              return (long) 1;          }          @Override         protected void onProgressUpdate(Integer... progress) {              progressDialog.setProgress(progress[0]);// 设置进度             super.onProgressUpdate(progress);             Log.e("测试", progress[0] + "");          }          @Override         protected void onPostExecute(Long result) {              setTitle(result + "测试");             textView1.setText(html);             progressDialog.dismiss();              super.onPostExecute(result);          }      }  } [java]package com.testasyntextview; /** * 使用Runable */ import android.app.Activity; import android.app.ProgressDialog; import android.content.Context; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.text.Html; import android.text.Spanned; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView;  public class RunableTestAsynTextViewActivity extends Activity {     private TextView textView1;     private Button button1;     private Context context;     private ProgressDialog progressDialog;     private Spanned html;      /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);         context = this;         textView1 = (TextView) findViewById(R.id.textView1);         button1 = (Button) findViewById(R.id.button1);         button1.setOnClickListener(l);      }      private OnClickListener l = new OnClickListener() {          @Override         public void onClick(View v) {              progressDialog = ProgressDialog.show(context, "获取数据中", "等待");             new Thread(new ThreadDemo()).start();          }     };      private void getHtmlDate() {         try {             html = HttpUtil.fromHtml(HttpUtil.getHtml("http://wap.sina.com"));         } catch (Exception e) {             e.printStackTrace();         }      }      class ThreadDemo implements Runnable {//一个runable         public void run() {             getHtmlDate();             myHandler.sendEmptyMessage(0);         }     }      Handler myHandler = new Handler() {          public void handleMessage(Message msg) {             switch (msg.what) {             case 0:                 textView1.setText(html);                 progressDialog.dismiss();                 break;             case 1:                 textView1.setText("当前无数据");                 progressDialog.dismiss();                 break;             }             super.handleMessage(msg);         }     };  } [java]package com.testasyntextview;  import java.io.ByteArrayOutputStream; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL;  import android.graphics.drawable.Drawable; import android.text.Html; import android.text.Spanned;  public class HttpUtil {     public static String getHtml(String path) throws Exception {         URL url = new URL(path);         HttpURLConnection conn = (HttpURLConnection) url.openConnection();         conn.setRequestMethod("GET");         conn.setConnectTimeout(5 * 1000);         InputStream inStream = conn.getInputStream();// 通过输入流获取html数据         byte[] data = readInputStream(inStream);// 得到html的二进制数据         String html = new String(data, "utf-8");         return html;     }      public static byte[] readInputStream(InputStream inStream) throws Exception {         ByteArrayOutputStream outStream = new ByteArrayOutputStream();         byte[] buffer = new byte[1024];         int len = 0;         while ((len = inStream.read(buffer)) != -1) {             outStream.write(buffer, 0, len);         }         inStream.close();         return outStream.toByteArray();     }      public static Spanned fromHtml(String html) {         Spanned sp = Html.fromHtml(html, new Html.ImageGetter() {             @Override             public Drawable getDrawable(String source) {                 InputStream is = null;                 try {                     is = (InputStream) new URL(source).getContent();                     Drawable d = Drawable.createFromStream(is, "src");                     d.setBounds(0, 0, d.getIntrinsicWidth(),                             d.getIntrinsicHeight());                     is.close();                     return d;                 } catch (Exception e) {                     return null;                 }             }         }, null);         return sp;      } }