如何使我的drawCircle向我的drawLine端点移动？

问题描述

我正在尝试使我的Projectile（drawCircle）朝着目标端点（drawLine aimX，aimY）向移动。我有一个方法movetowards，用于处理弹丸向端点的移动。您可以使用getY（）和getX（）方法通过滑动将端点拖出。我尝试使用斜率来获得上升并运行，使弹丸向端点移动，但是我不能将斜率用作小数。我也尝试使用有条件但无济于事的方法使射弹走向终点。到现在为止，无论我的端点是什么，我的弹丸都直接沿直线移动到某个位置。我在代码中使用注释，以专注于所有重要部分。

//MainActivity.java
package com.example.homework2_hakeemthomas;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Point;
import android.os.Bundle;
import android.os.Debug;
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    MyCanvas canvas;

    public static float slope =  0.0f;
    public static float xslope = 0.0f;
    public static float yslope = 0.0f;

    Point pointA;
    Point pointB;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        canvas = findViewById(R.id.canvas);

        canvas.setonTouchListener(fe);
    }

    //Moves the ball towards endpoint
    public void movetowards()
    {
        slope += 2;
    }
    @Override
    protected void onStart()
    {
        super.onStart();

        final Handler handler0 = new Handler();
        handler0.postDelayed(new Runnable() {
            public void run() {

                canvas.platformSpeed = canvas.platformSpeed + (2.0f * canvas.multiplier);
                //if the platform goes out of bound then flip the direction
                if(canvas.platformSpeed < 0 || canvas.platformSpeed > 600)
                {
                    canvas.multiplier *= -1;
                }

                if(canvas.isBallMoving)
                {
                    movetowards();
                }
                canvas.clearCanvas();
                canvas.invalidate();

                handler0.postDelayed(this,1);
            }
        },100);
    }

    private View.OnTouchListener fe = new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v,MotionEvent ev) {
            float invertedX = ev.getX();
            float y = ev.getY();

            int he = canvas.getMyBitmap().getHeight();
            int wd = canvas.getMyBitmap().getWidth();
            switch (ev.getAction())
            {
                case MotionEvent.ACTION_DOWN:
                    canvas.hasstarted = false;

                case MotionEvent.ACTION_MOVE:
                    
                    //Inverts for aiming like slingshot
                    canvas.aimX = wd - ev.getX();
                    canvas.aimY = he - ev.getY();
                    canvas.clearCanvas();
                    canvas.invalidate();

                    break;

                case MotionEvent.ACTION_UP:
                    canvas.isBallMoving = true;

                    canvas.aimY = y;

                    float y1 = (canvas.projectileY * canvas.myBitmap.getHeight());
                    float y2 = canvas.aimY;
                    float y3 = (y2 - y1);
                    float x1 = (canvas.projectileX * canvas.myBitmap.getWidth());
                    float x2 = canvas.aimX;
                    float x3 = (x2 - x1);

                    slope = (y3 / x3);
                    xslope = (y3 / slope);
                    yslope = (x3 * slope);
            }
            return false;
        }
    };
}

我的画布

//Canvas.java
package com.example.homework2_hakeemthomas;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.Region;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class MyCanvas extends View {

    private Paint pixelPaint;

    public Bitmap getMyBitmap() {
        return myBitmap;
    }

    private Paint myBitMapPaint;
    public Bitmap myBitmap;
    private Canvas myCanvas;

    private static int pixelPaintColor = Color.BLUE;

    //Holds the movement for all objects that apply
    public float projectileX = 0.2f,projectileY = 0.5f,projectileSize = 5.0f,platformX = 0.65f,platformY = 0.5f,aimX = 0.0f,aimY = 0.0f;

    public float platformSpeed = 0.0f;
    public float projectileSpeed = 0.0f;
    //Changes the platforms direction
    public int multiplier = 1;
    public MainActivity ma;

    public boolean hasstarted = true;
    public boolean isBallMoving = false;

    public MyCanvas(Context context,AttributeSet attrs)
    {
        super(context,attrs);

        myBitMapPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

        pixelPaint = new Paint();
        pixelPaint.setAntiAlias(true);
        pixelPaint.setStyle(Paint.Style.stroke);
        pixelPaint.setColor(pixelPaintColor);
        pixelPaint.setstrokeCap(Paint.Cap.ROUND);
        pixelPaint.setstrokeWidth(42);
    }

    @Override
    protected void onSizeChanged(int w,int h,int oldw,int oldh)
    {
        super.onSizeChanged(w,h,oldw,oldh);

        if(myBitmap == null)
        {
            myBitmap = Bitmap.createBitmap(w,Bitmap.Config.ARGB_8888);
            myCanvas = new Canvas(myBitmap);
        }
    }

    //Used to reset and move projectile
    public void clearCanvas() {
        myBitmap = Bitmap.createBitmap(myBitmap.getWidth(),myBitmap.getHeight(),Bitmap.Config.ARGB_8888);
        myCanvas = new Canvas(myBitmap);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);

        int w = myBitmap.getWidth();
        int h = myBitmap.getHeight();

        pixelPaint.setColor(Color.RED);
        pixelPaint.setstrokeWidth(60);

        //The Projectile
        myCanvas.drawCircle(((ma.slope + (w  * projectileX)) + projectileSpeed),(((h * projectileY) - ma.slope) + projectileSpeed),projectileSize,pixelPaint);
        
        if (hasstarted) {
            myCanvas.drawLine(w * (projectileX + 0.05f),h * projectileY,w * (aimX + .25f),h * (aimY + .5f),pixelPaint);
        }
        if(!isBallMoving && !hasstarted) {

            //The aimX and aimY are the endPoints
            myCanvas.drawLine(w * (projectileX + 0.05f),aimX,aimY,pixelPaint);
        }

        pixelPaint.setColor(Color.GREEN);
        myCanvas.drawRect((w * (platformX - .15f)) + platformSpeed,h * .5f,(w * platformX) + platformSpeed,h *.5f,pixelPaint);

        canvas.drawBitmap(myBitmap,myBitMapPaint);
    }
}

解决方法

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