在开发我们经常会使用到自定义实现控件， 今天呢就跟大家说一说switch开关按钮的自定义实现。

为了大家的方便，直接把代码贴出来，不想那么麻烦自己去写的朋友可以直接copy到你们的项目中使用哦，颜色、大小都可以根据自己的需求改一改就行啦!

下面贴出整个自定义类的代码：

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.os.Bundle;
import android.os.Looper;
import android.os.Parcelable;
import android.support.v4.view.MotionEventCompat;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.AccelerateDecelerateInterpolator;

public class SlideSwitcher extends View {

public static final int SHAPE_RECT = 1;
public static final int SHAPE_CIRCLE = 2;
private static final int RIM_SIZE = 4;
private static final int DEFAULT_OPEN_COLOR = 0xFFC80000;
private static final int DEFAULT_CLOSE_COLOR = 0xFFD0D0D0;

// 4 attributes
private int openColor;
private int closeColor;
private boolean isOpen;
private int shape;

// varials of drawing
private Paint paint;
private Rect backRect;
private Rect frontRect;
private RectF frontCircleRect;
private RectF backCircleRect;
private int alpha;
private int maxLeft;
private int minLeft;
private int frontRectLeft;
private int frontRectLeftBegin = RIM_SIZE;
private int eventStartX;
private int eventLastX;
private int diffX = 0;
private boolean slideable = true;
private SlideListener mSlideListener;

public interface SlideListener {
    void onStatusChanged(SlideSwitcher view, boolean isOpen);
}

public SlideSwitcher(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);

    paint = new Paint();
    paint.setAntiAlias(true);

    openColor = DEFAULT_OPEN_COLOR;
    closeColor = DEFAULT_CLOSE_COLOR;
    isOpen = false;
    shape = SHAPE_CIRCLE;
}

public SlideSwitcher(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public SlideSwitcher(Context context) {
    this(context, null);
}

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

    int width = measureDimension(280, widthMeasureSpec);
    int height = measureDimension(140, heightMeasureSpec);
    if (shape == SHAPE_CIRCLE) {
        if (width < height) width = height * 2;
    }
    setMeasuredDimension(width, height);
    initDrawingVal();
}

private void initDrawingVal() {
    int width = getMeasuredWidth();
    int height = getMeasuredHeight();

    backCircleRect = new RectF();
    frontCircleRect = new RectF();
    frontRect = new Rect();
    backRect = new Rect(0, 0, width, height);
    minLeft = RIM_SIZE;
    if (shape == SHAPE_RECT)
        maxLeft = width / 2;
    else
        maxLeft = width - (height - 2 * RIM_SIZE) - RIM_SIZE;
    if (isOpen) {
        frontRectLeft = maxLeft;
        alpha = 255;
    } else {
        frontRectLeft = RIM_SIZE;
        alpha = 0;
    }
    frontRectLeftBegin = frontRectLeft;
}

private int measureDimension(int defaultSize, int measureSpec) {
    int result;
    int specMode = MeasureSpec.getMode(measureSpec);
    int specSize = MeasureSpec.getSize(measureSpec);
    if (specMode == MeasureSpec.EXACTLY) {
        result = specSize;
    } else {
        result = defaultSize; // UNSPECIFIED
        if (specMode == MeasureSpec.AT_MOST) {
            result = Math.min(result, specSize);
        }
    }
    return result;
}

@Override
protected void onDraw(Canvas canvas) {
    if (shape == SHAPE_RECT) {
        paint.setColor(closeColor);
        canvas.drawRect(backRect, paint);
        paint.setColor(openColor);
        paint.setAlpha(alpha);
        canvas.drawRect(backRect, paint);
        frontRect
                .set(frontRectLeft, RIM_SIZE, frontRectLeft + getMeasuredWidth() / 2 - RIM_SIZE, getMeasuredHeight() - RIM_SIZE);
        paint.setColor(Color.WHITE);
        canvas.drawRect(frontRect, paint);
    } else {
        // draw circle
        int radius;
        radius = backRect.height() / 2;
        paint.setColor(closeColor);
        backCircleRect.set(backRect);
        canvas.drawRoundRect(backCircleRect, radius, radius, paint);
        paint.setColor(openColor);
        paint.setAlpha(alpha);
        canvas.drawRoundRect(backCircleRect, radius, radius, paint);
        frontRect.set(frontRectLeft, RIM_SIZE, frontRectLeft + backRect.height() - 2 * RIM_SIZE, backRect.height() - RIM_SIZE);
        frontCircleRect.set(frontRect);
        paint.setColor(Color.WHITE);
        canvas.drawRoundRect(frontCircleRect, radius, radius, paint);
    }
}

@SuppressLint("ClickableViewAccessibility")
@Override
public boolean onTouchEvent(MotionEvent event) {
    if (slideable == false)
        return super.onTouchEvent(event);
    int action = MotionEventCompat.getActionMasked(event);
    switch (action) {
        case MotionEvent.ACTION_DOWN:
            eventStartX = (int) event.getRawX();
            break;
        case MotionEvent.ACTION_MOVE:
            eventLastX = (int) event.getRawX();
            diffX = eventLastX - eventStartX;
            int tempX = diffX + frontRectLeftBegin;
            tempX = (tempX > maxLeft ? maxLeft : tempX);
            tempX = (tempX < minLeft ? minLeft : tempX);
            if (tempX >= minLeft && tempX <= maxLeft) {
                frontRectLeft = tempX;
                alpha = (int) (255 * (float) tempX / (float) maxLeft);
                invalidateView();
            }
            break;
        case MotionEvent.ACTION_UP:
            int wholeX = (int) (event.getRawX() - eventStartX);
            frontRectLeftBegin = frontRectLeft;
            boolean toRight;
            toRight = (frontRectLeftBegin > maxLeft / 2 ? true : false);
            if (Math.abs(wholeX) < 3) {
                toRight = !toRight;
            }
            moveToDest(toRight);
            break;
        default:
            break;
    }
    return true;
}

/**
 * draw again
 */
private void invalidateView() {
    if (Looper.getMainLooper() == Looper.myLooper()) {
        invalidate();
    } else {
        postInvalidate();
    }
}

public void setSlideListener(SlideListener listener) {
    this.mSlideListener = listener;
}

public void moveToDest(final boolean toRight) {
    ValueAnimator toDestAnim = ValueAnimator.ofInt(frontRectLeft, toRight ? maxLeft : minLeft);
    toDestAnim.setDuration(300);
    toDestAnim.setInterpolator(new AccelerateDecelerateInterpolator());
    toDestAnim.start();
    toDestAnim.addUpdateListener(new AnimatorUpdateListener() {

        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            frontRectLeft = (Integer) animation.getAnimatedValue();
            alpha = (int) (255 * (float) frontRectLeft / (float) maxLeft);
            invalidateView();
        }
    });
    toDestAnim.addListener(new AnimatorListenerAdapter() {
        @Override
        public void onAnimationEnd(Animator animation) {
            if (toRight) {
                isOpen = true;
                frontRectLeftBegin = maxLeft;
            } else {
                isOpen = false;
                frontRectLeftBegin = minLeft;
            }

            if (mSlideListener != null)
                mSlideListener.onStatusChanged(SlideSwitcher.this, isOpen);
        }
    });
}

public void setOpen(boolean isOpen) {
    setOpen(isOpen, false);
}

public void setOpen(boolean isOpen, boolean invokListener) {
    this.isOpen = isOpen;
    initDrawingVal();
    invalidateView();
    if (invokListener && mSlideListener != null) mSlideListener.onStatusChanged(this, isOpen);
}

public void setShapeType(int shapeType) {
    this.shape = shapeType;
}

public void setSlideable(boolean slideable) {
    this.slideable = slideable;
}

@Override
protected void onRestoreInstanceState(Parcelable state) {
    if (state instanceof Bundle) {
        Bundle bundle = (Bundle) state;
        this.isOpen = bundle.getBoolean("isOpen");
        state = bundle.getParcelable("instanceState");
    }
    super.onRestoreInstanceState(state);
}

@Override
protected Parcelable onSaveInstanceState() {
    Bundle bundle = new Bundle();
    bundle.putParcelable("instanceState", super.onSaveInstanceState());
    bundle.putBoolean("isOpen", this.isOpen);
    return bundle;
  }
}

下面是布局文件：

//在布局中使用
 <com.***.SlideSwitcher
            android:id="@+id/switch_btn"
            android:layout_width="48dp"
            android:layout_height="28dp"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true" />