Android 开发之 ToggleButton App 滑动开关按钮

现在很多项目都有推送这一块的功能，而用户不一定想看到这些推送，这时候开关按钮就是必须的了，让用户自己设置通知管理。android开发中我也自己写过一个自定义的view，虽然实现了效果不过感觉有点（动画效果）生硬，原理根据Touch 的距离和滑动速度判断开关，指向Toggle的回调函数，以及onClick执行相关毁掉。今日闲来无事，找到个比较满意的开关效果，github地址：https://github.com/zcweng/ToggleButton，效果图如下：

先看看自定义控件ToggleButton，该类调用了onDetachedFromWindow、onAttachedToWindow这两个方法，onAttachedToWindow方法作用是在自定义View

onDraw以前调用，用于绑定相关的监听事件，onDetachedFromWindow则想法，取消相关的监听事件。具体代码如下：

@Override
	protected void onDetachedFromWindow() {
		super.onDetachedFromWindow();
		spring.removeListener(springListener);
	}

	public void onAttachedToWindow() {
		super.onAttachedToWindow();
		spring.addListener(springListener);
	}

这里的springListener是自定义接口SimpleSpringListener ，根据string值重新计算出有效值，达到更新UI的目的 postInvalidate();实例化如下：

	SimpleSpringListener springListener = new SimpleSpringListener(){
		@Override
		public void onSpringUpdate(Spring spring) {
			final double value = spring.getCurrentValue();
			calculateEffect(value);
		}
	};

构造方法：

	public ToggleButton(Context context) {
		this(context,null);
	}
	public ToggleButton(Context context, AttributeSet attrs) {
		this(context, attrs,0);
	}
	public ToggleButton(Context context, AttributeSet attrs, int defStyleAttr) {
		super(context, attrs, defStyleAttr);
		setup(attrs);
	}

setup(attrs)这里通过TypedArray获取自定义属性值，变量重新赋值，同时绑定自身onClick事件到Toggle。

public void setup(AttributeSet attrs) {
		paint = new Paint(Paint.ANTI_ALIAS_FLAG);
		paint.setStyle(Style.FILL);
		paint.setStrokeCap(Cap.ROUND);

		springSystem = SpringSystem.create();
		spring = springSystem.createSpring();
		spring.setSpringConfig(SpringConfig.fromOrigamiTensionAndFriction(50, 7));

		this.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View arg0) {
				toggle(defaultAnimate);
			}
		});

		TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.ToggleButton);
		offBorderColor = typedArray.getColor(R.styleable.ToggleButton_offBorderColor, offBorderColor);
		onColor = typedArray.getColor(R.styleable.ToggleButton_onColor, onColor);
		spotColor = typedArray.getColor(R.styleable.ToggleButton_spotColor, spotColor);
		offColor = typedArray.getColor(R.styleable.ToggleButton_offColor, offColor);
		borderWidth = typedArray.getDimensionPixelSize(R.styleable.ToggleButton_borderWidth, borderWidth);
		defaultAnimate = typedArray.getBoolean(R.styleable.ToggleButton_animate, defaultAnimate);
		typedArray.recycle();

		borderColor = offBorderColor;
	}

Layout.xml应用自定义属性文件时需要注意，添加xmlns:toggle="http://schemas.android.com/apk/res-auto或者/res/com.zcw.togglebutton..自定义的属性文件：

接下来是自定义控件的测量onMeasure(int widthMeasureSpec, int heightMeasureSpec)方法重新测量View和内容，onMeasure方法调用就必须重新Measure保存测量到的宽高，否则measure会抛出异常。先来看看MeasureSpec:

 public static class MeasureSpec {
        private static final int MODE_SHIFT = 30;
        private static final int MODE_MASK  = 0x3 << MODE_SHIFT;

        /**
         * Measure specification mode: The parent has not imposed any constraint
         * on the child. It can be whatever size it wants.
         */
        public static final int UNSPECIFIED = 0 << MODE_SHIFT;

        /**
         * Measure specification mode: The parent has determined an exact size
         * for the child. The child is going to be given those bounds regardless
         * of how big it wants to be.
         */
        public static final int EXACTLY     = 1 << MODE_SHIFT;

        /**
         * Measure specification mode: The child can be as large as it wants up
         * to the specified size.
         */
        public static final int AT_MOST     = 2 << MODE_SHIFT;    ....此处省略

每个MeasureSpec都有一个Size和Mode，而Mode分三种：MeasureSpec.UNSPECIFIED、MeasureSpec.AT_MOST、MeasureSpec.EXACTLY。

unspecified:父布局对子布局没有任何限制，子布局可以是它想要的任何尺寸。exactly:父布局限制了子布局的绝对宽高，子布局将会被赋予这些边界限制.at-most:子布局可以是自己任意的大小，但是有个绝对尺寸的上限。下面来看看该类的onMeasure代码：

@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

		final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		final int heightMode = MeasureSpec.getMode(heightMeasureSpec);

		int widthSize = MeasureSpec.getSize(widthMeasureSpec);
		int heightSize = MeasureSpec.getSize(heightMeasureSpec);

		Resources r = Resources.getSystem();
		if(widthMode == MeasureSpec.UNSPECIFIED || widthMode == MeasureSpec.AT_MOST){
			widthSize = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 50, r.getDisplayMetrics());
			widthMeasureSpec = MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.EXACTLY);
		}

		if(heightMode == MeasureSpec.UNSPECIFIED || heightSize == MeasureSpec.AT_MOST){
			heightSize = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 30, r.getDisplayMetrics());
			heightMeasureSpec = MeasureSpec.makeMeasureSpec(heightSize, MeasureSpec.EXACTLY);
		}


		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
	}

接着调用OnLayout(int ,int ,int ,int)取出相对于父布局的上下左右的参数，重新计算View的摆放位置以及相关参数的配置。

	@Override
	protected void onLayout(boolean changed, int left, int top, int right,
			int bottom) {
		super.onLayout(changed, left, top, right, bottom);

		final int width = getWidth();
		final int height = getHeight();

		radius = Math.min(width, height) * 0.5f;
		centerY = radius;
		startX = radius;
		endX = width - radius;
		spotMinX = startX + borderWidth;
		spotMaxX = endX - borderWidth;
		spotSize = height - 4 * borderWidth;
		spotX = toggleOn ? spotMaxX : spotMinX;
		offLineWidth = 0;
	}

接下来就是onDraw视图的绘制了

@Override
	public void draw(Canvas canvas) {
		//
		rect.set(0, 0, getWidth(), getHeight());
		paint.setColor(borderColor);
		canvas.drawRoundRect(rect, radius, radius, paint);

		if(offLineWidth > 0){
			final float cy = offLineWidth * 0.5f;
			rect.set(spotX - cy, centerY - cy, endX + cy, centerY + cy);
			paint.setColor(offColor);
			canvas.drawRoundRect(rect, cy, cy, paint);
		}
                ............此处省略
		paint.setColor(spotColor);
		canvas.drawRoundRect(rect, spotR, spotR, paint);

	}

对于Paint的配置paint.setStrokeCap(Cap.ROUND); 画笔笔刷类型 如影响画笔但始末端， paint.setStrokeJoin(Paint.Join.ROUND); 画笔接洽点类型 如影响矩形但角的外轮廓，对于该项目setup里面springSystem这块理解不够透彻：

经过一番折腾，得到结果如下：“Choreographer就是一个消息处理器，根据vsync 信号 来计算frame，而计算frame的方式就是处理三种回调，包括事件回调、动画回调、绘制回调。这三种事件在消息输入、加入动画、准备绘图layout 等动作时均会发给Choreographer。”

 public static SpringLooper createSpringLooper() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
      return ChoreographerAndroidSpringLooper.create();
    } else {
      return LegacyAndroidSpringLooper.create();
    }
  }

这里项目走版本分支获取SpringLooper,从而注册BaseSpringSystem，在深入暂不涉及，参考相关资料：http://blog.csdn.net/farmer_cc/article/details/18619429,相关demo下载地址：http://download.csdn.net/detail/analyzesystem/8905455