android:progressbar实现进度条

在听网络音乐或者下载软件的时候总能看到进度条的身影 它是怎么实现的呢

应该是已下载的大小/总的应用的大小  哈哈 

progress小例子

布局文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="增加" />

    <Button
        android:id="@+id/sub"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="减少" />

    <Button
        android:id="@+id/reset"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="重置" />
    <Button
        android:id="@+id/show"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="显示进度条对话框" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:progress="20"
        android:secondaryProgress="30" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

</LinearLayout>

代码很简单

就不说了  主要的都有注释

package com.example.progressbar;

import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

  private Button button1;
  private Button button2;
  private Button button3;
  private Button show;
  private TextView textView;
  private ProgressBar progress, progress1;
  private ProgressDialog progressDialog;
  private int max;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    /*
     * 启用窗口特征，启用两种形式进度的进度条
     */
    requestWindowFeature(Window.FEATURE_PROGRESS);
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    setContentView(R.layout.activity_main);
    /*
     * 显示两种进度
     */
    //进度可见
    setProgressBarVisibility(true);
    //明确显示进度的
    setProgressBarIndeterminate(false);
    //最大进度为10000
    setProgress(3000);
    //进度可见
    setProgressBarIndeterminateVisibility(true);

    button1 = (Button) findViewById(R.id.add);
    button2 = (Button) findViewById(R.id.sub);
    button3 = (Button) findViewById(R.id.reset);
    show = (Button) findViewById(R.id.show);
    textView = (TextView) findViewById(R.id.textView1);
    progress = (ProgressBar) findViewById(R.id.progressBar);
    init();
    button1.setOnClickListener(this);
    button2.setOnClickListener(this);
    button3.setOnClickListener(this);
    show.setOnClickListener(this);

  }
  //初始化
  private void init() {
    // TODO Auto-generated method stub
    max = progress.getMax();
    progress.setProgress(50);
    progress.setSecondaryProgress(60);
    textView.setText("第一进度的百分比为" + (int)((float) progress.getProgress()
        / (float) max *100)+ "%,第二进度条的百分比为"
        + (int)((float) progress.getSecondaryProgress() / (float) max *100)+ "%");
  }

  @Override
  public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()) {
    //点击增加按钮  通过incrementProgressBy方法 增加进度
    case R.id.add:
      progress.incrementProgressBy(10);
      progress.incrementSecondaryProgressBy(10);
      break;
    //点击减少按钮  通过incrementProgressBy方法 减少进度
    case R.id.sub:
      progress.incrementProgressBy(-10);
      progress.incrementSecondaryProgressBy(-10);
      break;
    case R.id.reset:
      init();
      break;
    case R.id.show:
      progressDialog=new ProgressDialog(MainActivity.this);
      //设置对话框进度条的图标
      progressDialog.setIcon(R.drawable.ic_launcher);
      //设置对话框进度条的标题
      progressDialog.setTitle("苏苏爱自由");
      //设置对话框进度条的内容
      progressDialog.setMessage("欢迎进入苏苏的博客");
      //设置对话框进度条的显示风格
      progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
      //不是明确显示进度的
      progressDialog.setIndeterminate(true);
      //添加一个确定按钮 并为其添加事件
      progressDialog.setButton(DialogInterface.BUTTON_POSITIVE, "确定", new DialogInterface.OnClickListener() {
        
        @Override
        public void onClick(DialogInterface dialog, int which) {
          // TODO Auto-generated method stub
          Toast.makeText(MainActivity.this, "谢谢大家的支持", Toast.LENGTH_SHORT).show();
        }
      });
      //显示对话框进度条
      progressDialog.show();
      break;
    }
    textView.setText("第一进度的百分比为" + (int)((float) progress.getProgress()
        / (float) max *100)+ "%,第二进度条的百分比为"
        + (int)((float) progress.getSecondaryProgress() / (float) max *100)+ "%");
  }

}