了解开发手机的各项参数之UI大小_如何核查android中的ui大小-优快云博客

上一篇讲了获取显示屏的一些参数,那么今天说下怎么获得系统UI的一些参数.

下面是一个获取状态栏高度的例子.

public class MainActivity extends Activity {

	private TextView tv;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);	
		setContentView(R.layout.activity_main);
		
		try {
			
			//利用反射,获取framework层R类中的dimen类
			Class<?> classT = Class.forName("com.android.internal.R$dimen");
			//创建对象
			Object obj = classT.newInstance();
			
			//获取"status_bar_height"的索引字段
			Field field = classT.getField("status_bar_height");
			//获取"status_bar_height"的索引
			int id = field.getInt(obj);
			//获取"status_bar_height"的索引值,单位是px
			int pxStatusBar = getResources().getDimensionPixelSize(id);
			
			tv = (TextView)findViewById(R.id.show);
			tv.setText(" "+pxStatusBar);
			
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchFieldException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}
}

程序执行的结果就是 69,说明我手机的状态栏是69px.

说明:

//利用反射,获取framework层R类中的dimen类

Class<?> classT = Class.forName("com.android.internal.R$dimen");

我们知道,每一个安卓程序都会通过xml文件,生成一个R类,然后里面有String,id,layout等等静态类,每个子类

里面,就是相应的public static的字段.所以,只要我们知道了包名,就能获得该apk中绝大部分控件的大小.

也就是说,com.android.internal.R$dimen可以替换成别的apk的包名.

//获取"status_bar_height"的索引字段
Field field = classT.getField("status_bar_height");

这里的"status_bar_height"是从哪里获得的?

Android 2.3.5源代码更新至android 4.4，可以下载，度娘网盘

这里下载4.4.2的系统源码吧, 3.81G,记得解压到某个盘的根目录,否则可能文件夹名称长度超过限制导致部分文件失败.

mydroid\frameworks\base\core\res\res\values\dimen.xml文件

<resources>
    <!-- The width that is used when creating thumbnails of applications. -->
    <dimen name="thumbnail_width">164dp</dimen>
    <!-- The height that is used when creating thumbnails of applications. -->
    <dimen name="thumbnail_height">145dp</dimen>
    <!-- The standard size (both width and height) of an application icon that
         will be displayed in the app launcher and elsewhere. -->
    <dimen name="app_icon_size">48dip</dimen>
    <!-- The maximum number of action buttons that should be permitted within
         an action bar/action mode. This will be used to determine how many
         showAsAction="ifRoom" items can fit. "always" items can override this. -->
    <integer name="max_action_buttons">2</integer>
    <dimen name="toast_y_offset">64dip</dimen>
    <span style="color:#cc0000;"><!-- Height of the status bar -->
    <dimen name="status_bar_height">25dip</dimen></span>
    <!-- Height of the bottom navigation / system bar. -->
    <dimen name="navigation_bar_height">48dp</dimen>
    <!-- Height of the bottom navigation bar in portrait; often the same as @dimen/navigation_bar_height -->
    <dimen name="navigation_bar_height_landscape">48dp</dimen>
    <!-- Width of the navigation bar when it is placed vertically on the screen -->
    <dimen name="navigation_bar_width">42dp</dimen>
    <!-- Height of notification icons in the status bar -->
    <dimen name="status_bar_icon_size">24dip</dimen>
    <!-- Size of the giant number (unread count) in the notifications -->
    <dimen name="status_bar_content_number_size">48sp</dimen>
    <!-- Height of the system bar (combined status & navigation); used by
         SystemUI internally, not respected by the window manager. -->
    <dimen name="system_bar_height">@dimen/navigation_bar_height</dimen>

可以看到,这里有很多属性,包括:

然后:

int pxStatusBar = getResources().getDimensionPixelSize(id); = 69

之前的文章说过,我的屏幕密度是2.75, 所以 25*2.75 = 68.85.

如果用这一行:

float pxStatusBar = getResources().getDimension(id); = 68.85

因为我这个代码是谷歌的,有些手机会改这些默认值,不过看来我手机用的是默认的,没有改过.

总的来说,反射是个好东西,我这里仅仅是举了一个简单的例子,如果深入源码去发掘的话,还能做出更多有意思的东西.