<?xml version="1.0" encoding="utf-8"?>
 <selector xmlns:android="http://schemas.android.com/apk/res/android">
     <item android:drawable="@drawable/button_normal" /> <!-- default -->
     <item android:state_pressed="true"
           android:drawable="@drawable/button_pressed" /> <!-- pressed -->
     <item android:state_focused="true"
           android:drawable="@drawable/button_focused" /> <!-- focused -->
 </selector>

 XML file in your project res/drawable/ folder 

引用 ImageButton ( android:src attribute).

http://developer.android.com/intl/de/reference/android/widget/ImageButton.html

http://developer.android.com/intl/fr/reference/android/graphics/drawable/StateListDrawable.html

 styles 不能代码修改 theme可以动态修改

http://developer.android.com/intl/fr/guide/topics/ui/themes.html

res/drawable/my_button.xml

<?xml version="1.0" encoding="utf-8"?> 
<selector xmlns:android="http://schemas.android.com/apk/res/android"> 
  <item 
    android:state_pressed="true" 
    android:drawable="@drawable/btn_pressed" /> 
  <item 
    android:state_pressed="false" 
    android:drawable="@drawable/btn_normal" /> 
</selector> 
Button如此设置android:background="@drawable/my_button".

final Runnable r = new Runnable() 
{ 
    public void run()  
    { 
        tv.append("Hello World"); 
        handler.postDelayed(this, 1000); 
    } 
}; 
 
handler.postDelayed(r, 1000); 
Thread thread = new Thread() 
{ 
    @Override 
    public void run() {          try { 
            while(true) { 
                sleep(1000); 
                handler.post(r); 
            } 
        } catch (InterruptedException e) { 
            e.printStackTrace(); 
        } 
    } 
}; 
 
thread.start(); 
2.多线程图片

class DownloadImage extends AsyncTask<Void, Void, Drawable>{ 
        @Override 
        protected Drawable doInBackground(Void... params) { 
            return Util.getImageFromURL(/blog_article/imageURL/index.html);  
        } 
 
        @Override 
        protected void onPostExecute( Drawable d ) { 
            getImageIcon().setImageDrawable(d); 
        } 
 
} 
new DownloadImage().execute(); 

http://developer.android.com/intl/zh-CN/reference/android/os/AsyncTask.html

private static void downloadFile(String url, File outputFile) { 
  try {        URL u = new URL(/blog_article/url/index.html); 
      URLConnection conn = u.openConnection(); 
      int contentLength = conn.getContentLength(); 
 
      DataInputStream stream = new DataInputStream(u.openStream()); 
 
        byte[] buffer = new byte[contentLength]; 
        stream.readFully(buffer); 
        stream.close(); 
 
        DataOutputStream fos = new DataOutputStream(new FileOutputStream(outputFile)); 
        fos.write(buffer); 
        fos.flush(); 
        fos.close(); 
  } catch(FileNotFoundException e) { 
      return; // swallow a 404 
  } catch (IOException e) { 
      return; // swallow a 404 
  } 
}