在自定义View中使用自定义属性

自定义属性并使用

1在values目录下建立attrs.xml文件，在里面定义自己的属性，如下：

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="MyText">
        <attr name="lineNum" format="integer"/>
        <attr name="xScroll" format="boolean"/>
        <attr name="mStr" format="string"/>
    </declare-styleable>
</resources>

2在布局文件中使用自定义属性需要在根标签添加引用空间

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:mtext="http://schemas.android.com/apk/res/com.duduhali.customview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.duduhali.customview.MainActivity" >

    <com.duduhali.customview.view.MyText
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        mtext:lineNum="3"
        mtext:xScroll="true"
        mtext:mStr="你好自定义View" />

</RelativeLayout>

上面xmlns:mtext="http://schemas.android.com/apk/res/com.duduhali.customview"为添加引用空间。

mtext:lineNum="3"

mtext:xScroll="true"

mtext:mStr="你好自定义View"
为使用自定义属性。
要时自定的属性起作用，要在自己的View中加以引用，上面的MyText的构造函数如下，在里面对自定义属性加以使用

public MyText(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		TypedArray ta = context.obtainStyledAttributes(attrs,
				R.styleable.MyText);
		lineNum = ta.getInt(R.styleable.MyText_lineNum, 1);
		xScroll = ta.getBoolean(R.styleable.MyText_xScroll, false);
		text = ta.getString(R.styleable.MyText_mStr);
		if( text == null){//设置未设置此属性时的默认值
			text = "一只哈巴狗";
		}
		ta.recycle();//回收TypedArray,此后就不能再使用此TypedArray
	}

其中的lineNum和xScroll为整形，text为字符串

自定义View的基类和子类如下：

BaseView.java

public abstract class BaseView extends View {

	private boolean running = true;
	private MyThread thread;
	protected abstract void drawSub(Canvas canvas);//子类通过此方法此方法把元素画到界面上
	protected abstract void logic();//在调用子类的drawSub()方法前调用，实现对绘画元素的处理
	public BaseView(Context context) {//代码中生成view时调用
		super(context);
		// TODO Auto-generated constructor stub
	}

	public BaseView(Context context, AttributeSet attrs) {//布局文件中定义view调用
		super(context, attrs);
		// TODO Auto-generated constructor stub
	}
	
	public BaseView(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
		// TODO Auto-generated constructor stub
	}
	
	@Override
	protected final void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		if(thread == null){
			thread = new MyThread();
			thread.start();
		}else{
			drawSub(canvas);
		}
	}
	/*
	 * onDetachedFromWindow(),销毁view的时候调用，做收尾工作
	 * 相反，onAttachedToWindow()在第一次onDraw之前调用，只一次
	 */
	@Override
	protected void onDetachedFromWindow() {
		// TODO Auto-generated method stub
		running = false;
		super.onDetachedFromWindow();
	}

	class MyThread extends Thread{

		@Override
		public void run() {
			// TODO Auto-generated method stub
			while(running){
				logic();
				postInvalidate();
				try {
					Thread.sleep(30);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		
	}
}

MyText.java

public class MyText extends BaseView {

	private Paint paint = new Paint();
	private int lineNum = 0;
	private int mx = 0;
	private boolean xScroll = false;
	private String text;
	public MyText(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
	}

public MyText(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		TypedArray ta = context.obtainStyledAttributes(attrs,
				R.styleable.MyText);
		lineNum = ta.getInt(R.styleable.MyText_lineNum, 1);
		xScroll = ta.getBoolean(R.styleable.MyText_xScroll, false);
		text = ta.getString(R.styleable.MyText_mStr);
		if( text == null){//设置未设置此属性时的默认值
			text = "一只哈巴狗";
		}
		ta.recycle();//回收TypedArray,此后就不能再使用此TypedArray
	}

	@Override
	protected void drawSub(Canvas canvas) {//此方法把元素画到界面上
		// TODO Auto-generated method stub
		for(int i = 0; i < lineNum; i++ ){
			int textSize = 20 + i*10;
			paint.setTextSize(textSize);
			canvas.drawText(text, mx, textSize+textSize*i, paint);
		}
	}

	@Override
	protected void logic() {//在调用drawSub()前被父类调用，实现对绘画元素的处理
		// TODO Auto-generated method stub
		if( xScroll ){
			mx += 2;
			if( mx > getWidth() ){
				mx = (int) - paint.measureText(text);
				/*
				 * 获得字符串的现实宽度，必须是和context中资源相关联的,如：
				 * TextView tv = new TextView(getContext());
				 * Paint p = tv.getPaint();
				 * float width = p.measureText(text);
				 */			
			}
		}
	}

}

本demo是仿照极客学院上的案例做的

工程源码地址：http://download.csdn.net/detail/duduhali/9124585