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
