Android入门之进度条(ProgressBar)

package com.jkxqj.helloandroid;import android.app.Activity;import android.os.Bundle;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ProgressBar;public class MainActivity extends Activity {private ProgressBar progressBar;private Button firstButton;private Button secondButton;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);progressBar = (ProgressBar)findViewById(R.id.firstProgressBar);firstButton = (Button)findViewById(R.id.firstButton);secondButton = (Button)findViewById(R.id.secondButton);progressBar.setMax(100);firstButton.setOnClickListener(new FirstListener());secondButton.setOnClickListener(new SecondListener());}class FirstListener implements OnClickListener{@Overridepublic void onClick(View v) {progressBar.incrementProgressBy(10);}}class SecondListener implements OnClickListener{@Overridepublic void onClick(View v) {progressBar.incrementSecondaryProgressBy(20);}}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <Button        android:id="@+id/secondButton"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_alignLeft="@+id/firstProgressBar"        android:layout_below="@+id/firstButton"        android:layout_marginTop="26dp"        android:text="增加第二进度" />    <Button        android:id="@+id/firstButton"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_alignLeft="@+id/secondButton"        android:layout_below="@+id/firstProgressBar"        android:layout_marginTop="17dp"        android:text="增加第一进度" />    <ProgressBar        android:id="@+id/firstProgressBar"        style="?android:attr/progressBarStyleHorizontal"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_alignParentTop="true"        android:layout_centerHorizontal="true"        android:layout_marginTop="30dp" /></RelativeLayout>