異步加載數據的三種實現 – JAVA編程語言程序開發技術文章

[java] 
package com.testasyntextview; 
/**
 * 把獲取的線程寫到方法中(比較好)
 */ 
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, "獲取數據中", "等待"); 
            getHtmlDate(); 
 
        } 
    }; 
 
    private void getHtmlDate() {// 獲取數據,把線程寫入瞭其中 
        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("當前無數據"); 
                progressDialog.dismiss(); 
                break; 
            } 
            super.handleMessage(msg); 
        } 
    }; 
 

[java] 
package com.testasyntextview; 
 
/**
 * 使用AsyncTask類
 */ 
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("進度條"); 
        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) {// 獲取數據,把線程寫入瞭其中 
 
        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是結果 String 是入口參數 
 
            getHtmlDate(params[0]);// 可以運行兩個任務 
            publishProgress(50);// 發送進度50% 
            getHtmlDate(params[1]); 
            publishProgress(100);// 發送進度100% 
 
            return (long) 1; 
 
        } 
 
        @Override 
        protected void onProgressUpdate(Integer… progress) { 
 
            progressDialog.setProgress(progress[0]);// 設置進度 
            super.onProgressUpdate(progress); 
            Log.e("測試", progress[0] + ""); 
 
        } 
 
        @Override 
        protected void onPostExecute(Long result) { 
 
            setTitle(result + "測試"); 
            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, "獲取數據中", "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 {//一個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("當前無數據"); 
                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();// 通過輸入流獲取html數據 
        byte[] data = readInputStream(inStream);// 得到html的二進制數據 
        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; 
 
    } 

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