Android界面编程之六 第五组UI组件：ProgressBar及其子类

ProgressBar本身代表了进度条组件，它还派生了两个常用组件：SeekBar和RatingBar。

它和其子类在用法上十分相似，只是显示界面上有区别

2.6.1 ProgressBar的功能与用法

Android支持几种风格的进度条，通过style属性可以为ProgressBar指定风格。其支持的属性有：

@android:syle/Widget.ProgressBar.Horizontal	水平进度条
@android:syle/Widget.ProgressBar.Inverse	普通大小的环形进度条
@android:syle/Widget.ProgressBar.Large	大环形进度条
@android:syle/Widget.ProgressBar.Large.Inverse	大环形进度条
@android:syle/Widget.ProgressBar.Small	小环形进度条
@android:syle/Widget.ProgressBar.Small.Inverse	小环形进度条

除此之外，ProgressBar还支持如下常用XML属性：

android:max	设置该进度条的最大值
android:progress	设置该进度条的已完成进度
android:progressDrawable	设置该进度条的轨道对应的Drawable对象
android:indeterminate	若设为true，则进度条为不精确显示进度
android:indeterminateDrawable	设置绘制不显示进度条的Drawable对象
android:indeterminateDuration	设置不精确显示进度条的持续时间

android:progressDrawable用于指定进度条的轨道绘制形式，该属性可指定为一个LayerDrawable对象的引用（该对象可通过在XML文件中用<layer-list元素进行配置>）

setProgress(int)	设置进度的完成百分比
incrementProgressBy(int)	设置进度条的进度增加或减少（正负以区分）

示例代码：

public class MainActivity extends Activity {

private int [] data = new int [100];
int hasData = 0;
int status = 0;
ProgressBar bar , bar2 ;
Handler mHandler = new Handler()
{
@Override
public void handleMessage(Message msg)
{
if (msg. what == 0x11)
{
bar .setProgress( status );
bar2 .setProgress( status );
}
}
};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout. activity_main );
        bar = (ProgressBar) findViewById(R.id. bar );
        bar2 = (ProgressBar) findViewById(R.id. bar2 );
        //thread to process
        new Thread()
        {
        public void run()
        {
        while ( status < 100)
        {
        status = doWork();
        mHandler .sendEmptyMessage(0x111);
        }
        }
        }.start();
    }
    public int doWork()
    {
    data [ hasData ++] = ( int ) (Math.random() * 100);
    try
    {
    Thread.sleep(100);
    }
    catch (InterruptedException e)
    {
    e.printStackTrace();
    }
    return hasData ;

    }

}

main.xml代码：

< LinearLayout 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:orientation = "vertical"
>
< LinearLayout
    android:orientation = "horizontal"
    android:layout_width = "match_parent"
    android:layout_height = "wrap_content" >
< ProgressBar
    android:layout_width = "wrap_content"
    android:layout_height = "wrap_content"
    style = "@android:style/Widget.ProgressBar.Large" />
< ProgressBar
    android:layout_width = "wrap_content"
    android:layout_height = "wrap_content" />
< ProgressBar
    android:layout_width = "wrap_content"
    android:layout_height = "wrap_content"
    style = "@android:style/Widget.ProgressBar.Small" />
</ LinearLayout >
< TextView
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:text = "Progress of completion." />
< ProgressBar
    android:id = "@+id/bar"
    android:layout_width = "match_parent"
    android:layout_height = "wrap_content"
    android:max = "100"
    style = "@android:style/Widget.ProgressBar.Horizontal" />
< ProgressBar
    android:id = "@+id/bar2"
    android:layout_width = "match_parent"
    android:layout_height = "wrap_content"
    android:max = "100"
    android:progressDrawable = "@drawable/my_bar"
    style = "@android:style/Widget.ProgressBar.Horizontal" />

</ LinearLayout >

my_bar.xml代码；

<? xml version = "1.0" encoding = "utf-8" ?>
< layer-list xmlns:android = "http://schemas.android.com/apk/res/android" >
    < item android:id = "@android:id/background"
        android:drawable = "@drawable/no" />
    < item android:id = "@android:id/progress"
        android:drawable = "@drawable/ok" />

</ layer-list >

还有一种进度条，可以直接在标题上显示进度，这种进度条甚至不需要ProgressBar，它直接由Activity启用，使用步骤如下：

1.调用Activity的requestWindowFeature()方法

2.setProgressBarVisibility(boolean)或者setProgressBarIndeterminateVisibility(boolean)方法控制显示和隐藏

示例代码如下：

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        //progress bar on title
        requestWindowFeature(Window. FEATURE_PROGRESS );
        requestWindowFeature(Window. FEATURE_INDETERMINATE_PROGRESS );
        setContentView(R.layout. activity_main );
        Button bn1 = (Button) findViewById(R.id. bn1 );
        Button bn2 = (Button) findViewById(R.id. bn2 );
        bn1.setOnClickListener( new OnClickListener()
        {
        @Override
        public void onClick(View source)
        {
        setProgressBarIndeterminateVisibility( true );
        setProgressBarVisibility( true );
        setProgress(4500);
        }
        });

        bn2.setOnClickListener( new OnClickListener()
        {
        @Override
        public void onClick(View source)
        {
        setProgressBarIndeterminateVisibility( false );
        setProgressBarVisibility( false );
        }
        });

    }

}

2.6.2 SeekBar的功能和用法 （拖动条）

SeekBar继承了ProgressBar，故ProgressBar所支持的XML属性和方法适用于SeekBar

SeekBar允许用户改变拖动条的滑块外观，改变滑块外观通过如下属性来指定：

android:thumb 指定一个Drawable对象，作为自定义滑块

2.6.3 RatingBar的功能和用法（ 星级评分条 ）

星级评分条与拖动条有相同的父类：AbsSeekBar

唉3是android:isIndicator	设置该星级评分条是否允许用户改变（true为不允许修改）
android:numStars	共有多少星级
android:rating	默认评分星级
android:stepSize	每次需要改变多少个星级

为了让程序响应星级评分条的改变，程序可为其绑定一个OnRatingBarChangeListenter监听器

示例代码：

public class MainActivity extends ActionBarActivity {

RatingBar ratingBar ;
ImageView image ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout. activity_main );
        ratingBar = (RatingBar) findViewById(R.id. rating );
        image = (ImageView) findViewById(R.id. iamge );
        ratingBar .setOnRatingBarChangeListener( new OnRatingBarChangeListener()
        {
        @Override
        public void onRatingChanged(RatingBar arg0, float rating, boolean fromUser)
        {
        image .setAlpha(( int )(rating * 255/5));
        }
        });

    }

xml代码：

< LinearLayout 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:orientation = "vertical" >

    < ImageView
        android:id = "@+id/iamge"
        android:layout_width = "match_parent"
        android:layout_height = "240px"
        android:src = "@drawable/lijiang"
        />
    < RatingBar
        android:id = "@+id/rating"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:numStars = "5"
        android:max = "255"
        android:progress = "255"
        android:stepSize = "0.5"
        />

</ LinearLayout >