自定义View随手指拖动进行移动

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package com.wuxinle.touchimageview.utils;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;

/**
 * @author: ding xujun
 * @created on: 2019/3/25 11:12
 * @project: TouchImageView-master
 */
public class DrawView1 extends View {

    private Context context;
    private int x = 100;
    private int y = 100;
    private int radius = 100;
    private Paint mpaint;
    private int width;
    private int height;

    public DrawView1(Context context) {
        super(context);
        this.context = context;
        init();
    }

    public DrawView1(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public DrawView1(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawCircle(x, y, radius, mpaint);
        System.out.println("---------canvas");
    }
    private void init() {
        mpaint = new Paint();
        mpaint.setColor(Color.RED);
        mpaint.setAntiAlias(true);
        WindowManager manager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
        width = manager.getDefaultDisplay().getWidth();
        height = manager.getDefaultDisplay().getHeight();

    }

    private int lastx;
    private int lastY;


    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                break;
            case MotionEvent.ACTION_MOVE:
                x = (int) event.getX();
                y = (int) event.getY();
                if (x >= 100 && y >= 100 && x <= width - 100 && y <= height - 300) {
                    if (Math.abs(x - lastx) <= 200 && Math.abs(y - lastY) <= 200) {
                        postInvalidate();
                        lastx = x;
                        lastY = y;
                    }

                }
                break;
            case MotionEvent.ACTION_UP:
                break;
        }
        return true;
    }

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

使用：

package com.wuxinle.touchimageview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.wuxinle.touchimageview.utils.DrawView1;

public class Main2Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        DrawView1 drawView1 =new DrawView1(getBaseContext());
        setContentView(drawView1);
    }
}