Android实现类似ios滑动按钮

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:id="@ id/activity_switch_button"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:paddingBottom="@dimen/activity_vertical_margin"
  android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  tools:context="com.example.app_switchbutton.SwitchButtonActivity">
 
  <com.example.app_switchbutton.switchbutton
    android:id="@ id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true" />
  <com.example.app_switchbutton.switchbutton
    android:layout_width="100dp"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_alignParentBottom="true"/>
 
</RelativeLayout>

package com.example.app_switchbutton;
 
import android.animation.ValueAnimator;
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.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.RadioButton;
 
/**
 * Created by 尽途 on 2017/4/26.
 */
 
public class switchbutton extends View {
  private int widthSize;
  private int heightSize;
  private boolean isOn=false;
  private float WhiteRoundRect_width,WhiteRoundRect_height;
  private float Circle_X,Circle_Y,WhiteRoundRect_X,WhiteRoundRect_Y;
  private float Radius;
  private float currentValue;
  private int currentAlphaofGreen,currentAlphaofGray;
  public switchbutton(Context context){
    super(context);
  }
  public switchbutton(Context context, AttributeSet attributeSet){
    super(context,attributeSet);
    setLayerType(LAYER_TYPE_SOFTWARE,null);
    initData();
  }
 
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    widthSize=MeasureSpec.getSize(widthMeasureSpec);
    heightSize=(int)(widthSize*0.65f);
    setMeasuredDimension(widthSize,heightSize);
    initData();
  }
  void initData(){
    if (isOn){
      currentValue=widthSize-0.5f*heightSize;
      currentAlphaofGreen=255;
      currentAlphaofGray=0;
    }
    else {
      currentValue=0.5f*heightSize;
      currentAlphaofGreen=0;
      currentAlphaofGray=255;
    }
  }
 
  @Override
  protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
  }
 
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (isOn){
      DrawBackGreenRoundRect(canvas);
      DrawCircle(canvas);
    }
    else {
      DrawBackGrayRoundRect(canvas);
      DrawBackWhiteRoundRect(canvas);
      DrawCircle(canvas);
    }
  }
  private void DrawBackGrayRoundRect(Canvas canvas){
    Paint paint0=new Paint();
    paint0.setStyle(Paint.Style.FILL);
    paint0.setColor(Color.GRAY);
    paint0.setAntiAlias(true);
    paint0.setAlpha(currentAlphaofGray);
    RectF roundRect=new RectF(0,0,widthSize,heightSize);
    canvas.drawRoundRect(roundRect,heightSize*0.5f,heightSize*0.5f,paint0);
  }
  private void DrawBackGreenRoundRect(Canvas canvas){
    Paint paint1=new Paint();
    paint1.setStyle(Paint.Style.FILL);
    paint1.setColor(Color.GREEN);
    paint1.setAntiAlias(true);
    paint1.setAlpha(currentAlphaofGreen);
    RectF roundRect=new RectF(0,0,widthSize,heightSize);
    canvas.drawRoundRect(roundRect,heightSize*0.5f,heightSize*0.5f,paint1);
  }
  private void DrawCircle(Canvas canvas){
    Circle_Y=heightSize*0.5f;
    Radius=heightSize*0.45f;
    Paint paint2=new Paint();
    paint2.setStyle(Paint.Style.FILL);
    paint2.setColor(Color.WHITE);
    paint2.setAntiAlias(true);
    canvas.drawCircle(currentValue,Circle_Y,Radius,paint2);
  }
  private void DrawBackWhiteRoundRect(Canvas canvas){
    Paint paint3=new Paint();
    paint3.setStyle(Paint.Style.FILL);
    paint3.setColor(Color.RED);
    paint3.setAntiAlias(true);
    paint3.setAlpha(currentAlphaofGray);
    WhiteRoundRect_X=heightSize*0.05f;
    WhiteRoundRect_Y=heightSize*0.05f;
    WhiteRoundRect_width=widthSize-0.05f*heightSize;
    WhiteRoundRect_height=heightSize*0.95f;
    RectF rectf=new RectF(WhiteRoundRect_X,WhiteRoundRect_Y,WhiteRoundRect_width,WhiteRoundRect_height);
    canvas.drawRoundRect(rectf,WhiteRoundRect_height*0.5f,WhiteRoundRect_height*0.5f,paint3);
  }
 
  /**
   * 添加了过渡值动画，实现了平缓运动
   * @param startValue
   * @param endValue
   */
  private void setAnimation(float startValue,float endValue){
    ValueAnimator valueAnimator=ValueAnimator.ofFloat(startValue,endValue);
    valueAnimator.setDuration(1500);
    valueAnimator.setTarget(currentValue);
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        currentValue=(float)animation.getAnimatedValue();
        invalidate();
      }
    });
    valueAnimator.start();
  }
  private void setAlphaAnimationofGray(int startValue,int endValue){
    ValueAnimator valueAnimator=ValueAnimator.ofInt(startValue,endValue);
    valueAnimator.setDuration(1500);
    valueAnimator.setTarget(currentAlphaofGray);
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        currentAlphaofGray=(int)animation.getAnimatedValue();
        invalidate();
      }
    });
    valueAnimator.start();
  }
  private void setAlphaAnimationofGreen(int startValue,int endValue){
    ValueAnimator valueAnimator=ValueAnimator.ofInt(startValue,endValue);
    valueAnimator.setDuration(1500);
    valueAnimator.setTarget(currentAlphaofGreen);
    valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        currentAlphaofGreen=(int)animation.getAnimatedValue();
        invalidate();
      }
    });
    valueAnimator.start();
  }
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()){
      case MotionEvent.ACTION_DOWN:
        return true;
      case MotionEvent.ACTION_MOVE:
        return false;
      case MotionEvent.ACTION_UP:
        isOn=!isOn;
        invalidate();
        break;
      default:
        break;
    }
    if (isOn){
      float startCircle_X=0.5f*heightSize;
      float endCircle_X=widthSize-0.5f*heightSize;
      setAnimation(startCircle_X,endCircle_X);
      setAlphaAnimationofGray(255,0);
      setAlphaAnimationofGreen(0,255);
    }else {
      float startCircle_X=widthSize-0.5f*heightSize;
      float endCircle_X=heightSize*0.5f;
      setAnimation(startCircle_X,endCircle_X);
      setAlphaAnimationofGray(0,255);
      setAlphaAnimationofGreen(255,0);
 
    }
    return super.onTouchEvent(event);
  }
  public void writeSwitchButtonState(boolean isOn){
    this.isOn=isOn;
  }
  public boolean readSwitchButtonState(){
    return isOn;
  }
}