android 自定义view--点击屏幕生成圆点，点击圆点可以拖动

package com.minibox.mycpp;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.util.Log;import android.view.GestureDetector;import android.view.MotionEvent;import android.view.View;import java.util.ArrayList;import java.util.List;import androidx.annotation.Nullable;/** * Created by lingbeijing on 2020/9/5. */public class DragBoll extends View implements GestureDetector.OnGestureListener {             private Paint mPaint;    private float point_x;    private float point_y;    private final float radio = 43.0f;    private RectF targetRectF;    private List<RectF> mCircles;        private GestureDetector mDetector;    public DragBoll(Context context) {             super(context);    }    public DragBoll(Context context, @Nullable AttributeSet attrs) {             this(context, attrs,0);    }    public DragBoll(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {             this(context, attrs, defStyleAttr,0);    }    public DragBoll(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {             super(context, attrs, defStyleAttr, defStyleRes);        init();    }    @Override    public boolean onTouchEvent(MotionEvent event) {             if(mDetector.onTouchEvent(event)){                 return true;        }        switch (event.getAction()){                 case MotionEvent.ACTION_DOWN:                targetRectF = getTarget(event);                break;            case MotionEvent.ACTION_MOVE:                point_x = event.getX();                point_y = event.getY();                //在触摸点位置为中心绘制圆                Log.i("lingbj", "draw:");                if(targetRectF != null) {                         targetRectF.left = point_x - radio;                    targetRectF.right = point_x + radio;                    targetRectF.bottom = point_y + radio;                    targetRectF.top = point_y - radio;                    invalidate();                                    }                break;            case MotionEvent.ACTION_CANCEL:                point_x = 0;                point_y = 0;                targetRectF = null;                invalidate();                break;        }        return true;    }    private void init(){             mPaint = new Paint();        mCircles = new ArrayList<>();        mDetector = new GestureDetector(getContext(),this);        mPaint.setAntiAlias(true);        mPaint.setColor(Color.GREEN);        mPaint.setStrokeWidth(5);        mPaint.setStyle(Paint.Style.FILL_AND_STROKE);    }    private RectF getTarget(MotionEvent event){             for(RectF rect: mCircles){                 if(rect.contains(event.getX(), event.getY())) {                     return rect;            }        }        return null;    }    @Override    public void draw(Canvas canvas) {             super.draw(canvas);        for (RectF rect : mCircles) {                 canvas.drawRoundRect(rect, radio, radio, mPaint);        }    }    @Override    public boolean onDown(MotionEvent motionEvent) {             return false;    }    @Override    public void onShowPress(MotionEvent motionEvent) {         }    @Override    public boolean onSingleTapUp(MotionEvent motionEvent) {             Log.i("lingbj", "onSingleTapUp");        if (mCircles.size() < 10) {                 float x = motionEvent.getX();            float y = motionEvent.getY();            RectF rectF = new RectF();            rectF.left = x - radio;            rectF.right = x + radio;            rectF.bottom = y + radio;            rectF.top = y - radio;            mCircles.add(rectF);            invalidate();        }        return true;    }    @Override    public boolean onScroll(MotionEvent motionEvent, MotionEvent motionEvent1, float v, float v1) {             return false;    }    @Override    public void onLongPress(MotionEvent motionEvent) {         }    @Override    public boolean onFling(MotionEvent motionEvent, MotionEvent motionEvent1, float v, float v1) {             return false;    }}
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