Android控件之ProgressBar探究

    ProgressBar位于android.widget包下，其继承于View，主要用于显示一些操作的进度。应用程序可以修改其长度表示当前后台操作的完成情况。因为进度条会移动，所以长时间加载某些资源或者执行某些耗时的操作时，不会使用户界面失去响应。ProgressBar类的使用非常简单，只需将其显示到前台，然后启动一个后台线程定时更改表示进度的数值即可。

以下ProgressBar跟Handle结合，模拟进度条的使用，当进度条完成时会跳转到TestActivity

main.xml布局文件

  
    

   
     <?
   
     xml version
   
     =
   
     "
   
     1.0
   
     "
   
      encoding
   
     =
   
     "
   
     utf-8
   
     "
   
     ?>
   
     

   
     <
   
     LinearLayout xmlns:android
   
     =
   
     "
   
     http://schemas.android.com/apk/res/android
   
     "
   
     
 android:orientation
   
     =
   
     "
   
     vertical
   
     "
   
      
 android:layout_width
   
     =
   
     "
   
     fill_parent
   
     "
   
     
 android:layout_height
   
     =
   
     "
   
     fill_parent
   
     "
   
     >
   
     
 
   
     <!--
   
      长方形进度条，一开始不可见，直到点击按钮时才出现进度条 
   
     -->
   
     
 
   
     <
   
     ProgressBar android:id
   
     =
   
     "
   
     @+id/progressBar
   
     "
   
     
 style
   
     =
   
     "
   
     ?android:attr/progressBarStyleHorizontal
   
     "
   
     
 mce_style
   
     =
   
     "
   
     ?android:attr/progressBarStyleHorizontal
   
     "
   
     
 android:layout_width
   
     =
   
     "
   
     fill_parent
   
     "
   
     
 android:layout_height
   
     =
   
     "
   
     wrap_content
   
     "
   
     
 android:visibility
   
     =
   
     "
   
     gone
   
     "
   
     
 android:max
   
     =
   
     "
   
     100
   
     "
   
      
   
     />
   
     
 
   
     <!--
   
      圆形进度条 
   
     -->
   
     
 
   
     <!--<
   
     ProgressBar android:id
   
     =
   
     "
   
     @+id/progressBar
   
     "
   
     
 style
   
     =
   
     "
   
     ?android:attr/progressBarStyleLarge
   
     "
   
     
 mce_style
   
     =
   
     "
   
     ?android:attr/progressBarStyleLarge
   
     "
   
     
 android:layout_width
   
     =
   
     "
   
     wrap_content
   
     "
   
     
 android:layout_height
   
     =
   
     "
   
     wrap_content
   
     "
   
      
   
     />-->
   
     
 
   
     <
   
     Button android:id
   
     =
   
     "
   
     @+id/start
   
     "
   
      
 android:text
   
     =
   
     "
   
     启动进度条
   
     "
   
     
 android:layout_width
   
     =
   
     "
   
     wrap_content
   
     "
   
     
 android:layout_height
   
     =
   
     "
   
     wrap_content
   
     "
   
      
   
     />
   
     
 
   
     <
   
     Button android:id
   
     =
   
     "
   
     @+id/stop
   
     "
   
      
 android:text
   
     =
   
     "
   
     停止进度条
   
     "
   
     
 android:layout_width
   
     =
   
     "
   
     wrap_content
   
     "
   
     
 android:layout_height
   
     =
   
     "
   
     wrap_content
   
     "
   
      
   
     />
   
     

   
     </
   
     LinearLayout
   
     >
  
    

PbActivity类

  
    

   
     package
   
      com.ljq.pb;


   
     import
   
      android.app.Activity;

   
     import
   
      android.content.Intent;

   
     import
   
      android.os.Bundle;

   
     import
   
      android.os.Handler;

   
     import
   
      android.view.View;

   
     import
   
      android.widget.Button;

   
     import
   
      android.widget.ProgressBar;


   
     public
   
      
   
     class
   
      PbActivity 
   
     extends
   
      Activity {
 
   
     private
   
      ProgressBar progressBar 
   
     =
   
      
   
     null
   
     ;
 
   
     private
   
      Button start 
   
     =
   
      
   
     null
   
     , stop 
   
     =
   
      
   
     null
   
     ;
 
   
     //
   
      定义Handler对象
   
     

   
      
   
     private
   
      Handler handler 
   
     =
   
      
   
     new
   
      Handler();


 @Override
 
   
     public
   
      
   
     void
   
      onCreate(Bundle savedInstanceState) {
 
   
     super
   
     .onCreate(savedInstanceState);
 setContentView(R.layout.main);

 progressBar 
   
     =
   
      (ProgressBar) findViewById(R.id.progressBar);
 progressBar.setProgress(
   
     0
   
     );
 
 start 
   
     =
   
      (Button) findViewById(R.id.start);
 start.setOnClickListener(
   
     new
   
      View.OnClickListener() {

 
   
     public
   
      
   
     void
   
      onClick(View v) {
 handler.post(runnable); 
   
     //
   
     开始执行
   
     

   
      }
 
 });
 stop
   
     =
   
     (Button)findViewById(R.id.stop);
 stop.setOnClickListener(
   
     new
   
      View.OnClickListener() {

 
   
     public
   
      
   
     void
   
      onClick(View v) {
 handler.removeCallbacks(runnable);
   
     //
   
     停止执行
   
     

   
      progressBar.setProgress(
   
     0
   
     );
 }
 
 });
 }

 
   
     int
   
      pro
   
     =
   
     0
   
     ;
 Runnable runnable
   
     =
   
     new
   
      Runnable(){
 
   
     public
   
      
   
     void
   
      run() {
 progressBar.setVisibility(View.VISIBLE);
 pro
   
     =
   
     progressBar.getProgress()
   
     +
   
     10
   
     ;
 progressBar.setProgress(pro);
 
   
     //
   
     如果进度小于100,，则延迟1000毫秒后重复执行runnable
   
     

   
      
   
     if
   
     (pro
   
     <
   
     100
   
     ){
 handler.postDelayed(runnable, 
   
     1000
   
     );
 }
   
     else
   
     {
 progressBar.setVisibility(View.GONE);
 startActivity(
   
     new
   
      Intent(PbActivity.
   
     this
   
     , TestActivity.
   
     class
   
     ));
 handler.removeCallbacks(runnable);
 progressBar.setProgress(
   
     0
   
     );
 }
 }
 };
}
  
    

运行结果