自定义控件_绘制太极(拖动)

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import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

/**
 * Created by Administrator on 2017/4/17.
 */
public class MyView extends View{
    private static final String TAG = "TJView";
    private int padding = 8;
    //画笔工具
    private Paint mPaint;
    //圆心坐标
    private float currentX = 0;
    private float currentY = 0;
    //大圆半径
    private float radiusBig = 200;
    //中圆半径
    private float radiusCenter = radiusBig / 2;
    //小圆半径
    private float radiusSmall = radiusCenter / 3;
    private int width;
    private int height;
    private float distance;
    private final float increment = 10;
    private final float min = 50;
    public MyView(Context context) {
        this(context, null);
    }

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

    public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
       // setAnimation();
    }

    /**
     * 设置缩放动画
     */
    /*private void setAnimation() {
        ScaleAnimation scaleAnimation2 = new ScaleAnimation(0.7f, 1.0f, 0.7f, 1.0f, ScaleAnimation.RELATIVE_TO_PARENT, 0.5f, ScaleAnimation.RELATIVE_TO_PARENT, 0.5f);
        scaleAnimation2.setDuration(500);// 设置持续时间
        scaleAnimation2.setRepeatCount(99999);// 设置重复次数
        scaleAnimation2.setFillAfter(true);// 保持动画结束时的状态
        startAnimation(scaleAnimation2);
    }*/

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        drawBg(canvas);
        drawLeftHalfCirle(canvas);
        drawTBCirle(canvas);
    }

    /**
     * 画上下两个圆--中圆和小圆
     *
     * @param canvas
     */
    private void drawTBCirle(Canvas canvas) {
        //画上面的白中圆
        mPaint.setColor(Color.WHITE);
        canvas.drawCircle(currentX, currentY - radiusBig / 2, radiusCenter, mPaint);
        //画上面的黑小圆
        mPaint.setColor(Color.BLACK);
        canvas.drawCircle(currentX, currentY - radiusBig / 2, radiusSmall, mPaint);
        //画下面的黑中圆
        mPaint.setColor(Color.BLACK);
        canvas.drawCircle(currentX, currentY + radiusBig / 2, radiusCenter, mPaint);
        //画下面的白小圆
        mPaint.setColor(Color.WHITE);
        canvas.drawCircle(currentX, currentY + radiusBig / 2, radiusSmall, mPaint);
    }

    /**
     * 画左边半圆
     *
     * @param canvas
     */
    private void drawLeftHalfCirle(Canvas canvas) {
        mPaint.setColor(Color.WHITE);
        canvas.drawArc(new RectF(currentX - radiusBig, currentY - radiusBig, currentX + radiusBig, currentY + radiusBig), 90, 180, true, mPaint);//90度开始画180度
    }

    /**
     * 画黑色的背景底板
     *
     * @param canvas
     */
    private void drawBg(Canvas canvas) {
        mPaint.setColor(Color.BLACK);
        canvas.drawCircle(currentX, currentY, radiusBig + padding, mPaint);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        currentX = MeasureSpec.getSize(widthMeasureSpec) / 2;
        currentY = MeasureSpec.getSize(heightMeasureSpec) / 2;
        setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
        width = getWidth();
        height = getHeight();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        /*currentX = event.getX();
        currentY = event.getY();
        invalidate();
        return true;*/
        //手指的数量
        int count = event.getPointerCount();
        float x = event.getX();
        float y = event.getY();
        int action = event.getAction();
        if(action==MotionEvent.ACTION_POINTER_DOWN){
            distance = getDistance(event);
        }
        if(count==1) {
            if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_MOVE) {
                if (x > width - radiusBig) {
                    x = width - radiusBig;
                } else if (x < radiusBig) {
                    currentX = radiusBig;
                } else {
                    currentX = x;
                }
                if (y > height - radiusBig) {
                    currentY = height - radiusBig;
                } else if (y < radiusBig) {
                    currentY = radiusBig;
                } else {
                    currentY = y;
                }
                postInvalidate();
            }
        }
        else if(count==2&&action == MotionEvent.ACTION_MOVE){

            float maxR = 0;

            if(currentX<currentY){
                maxR = currentX;
            }else{
                maxR = currentY;
            }

            //判断手指方向
            if(distance>getDistance(event)){
                radiusBig -= increment;
                if(radiusBig<min){
                    radiusBig = min;
                }
            }else if(distance<getDistance(event)){
                radiusBig += increment;
                if(radiusBig>maxR){
                    radiusBig = maxR;
                }else if(radiusBig>width/2){
                    radiusBig = width/2;
                }
            }
            distance = getDistance(event);
            postInvalidate();
        }
        return true;
    }
    private float getDistance(MotionEvent event){

        float xOne = event.getX(0);
        float yOne = event.getY(0);
        float xTwo = event.getX(1);
        float yTwo = event.getY(1);
        return (xOne - xTwo)*(xOne - xTwo)+(yOne - yTwo)*(yOne - yTwo);
    }
}