如何在屏幕上获取触摸位置 (Android)

Question

我正在用 android 开发游戏，在那个游戏中我使用画布来显示网格 (5*6) 的圆圈。 我想检查触控区域的位置。例如，如果我在两个相邻圆圈周围触摸/点击屏幕，它应该返回位置，或者如果可能的话，它应该显示这些圆圈之间的线。为此，我使用了这个 onTouchEvent() 方法。但我没有在我的设备屏幕上获得任何输出。我已经在 Stackoverflow 上检查了那里给出的方法，但它对我没有帮助，这是链接（How to get the Touch position in android?）。我要求您检查此代码并提出解决方案。这是代码文件：

   package com.example.tap;

import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.gesture.Gesture;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.Log;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new board(this));
    }

    public class board extends View
    {
        Paint pBack = new Paint();
        Paint pDot  = new Paint();
        int xpos=0;
        int ypos=0;

        int cols = 5;
        int rows = 6;

        public board(Context context)
        {
            super(context);
            pBack.setARGB(255, 15, 102, 0);
            pDot.setARGB(255, 255, 255, 255);
        }

        @SuppressLint("DrawAllocation")
        protected void onDraw(Canvas canvas)
        {
            super.onDraw(canvas);
            canvas.drawPaint(pBack);
            float xStep = canvas.getWidth() / (cols + 1);
            float yStep = canvas.getHeight() / (rows + 1);
            float curCirclXpos, curCirclYpos, lastCirclXpos = 0, lastCirclYpos =0;
            //float vertical= 
//          boolean onTap(Gesture g, Point p)
//          {
//              
//          }

            for (int y = 0; y < rows; y++)
            {
                for (int x = 0; x < cols; x++)
                {
                    canvas.drawCircle((x + 1) * xStep, (y + 1) * yStep, 20, pDot);
                    curCirclXpos=x;
                    curCirclYpos=y;

                    if (y == 0)
                    {
                        //canvas.drawLine((x + 1) * xStep, yStep, (x + 1) * xStep, rows * yStep, pDot);
                        //canvas.drawLine(xpos, ypos, xpos, yStep, pDot);
                        canvas.drawLine(curCirclXpos, curCirclYpos, lastCirclXpos, lastCirclYpos, pDot);
                    }                   
                }

                //canvas.drawLine(xStep, (y + 1) * yStep, cols * xStep, (y + 1) * yStep, pDot);
            }
        }
        public boolean onTouchEvent(MotionEvent e)
        {
            xpos=(int) e.getX();
           ypos=(int) e.getY();
            switch (e.getAction())
            {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_MOVE:
                //Log.d("Umar",String.valueOf(xpos));
                //Log.d("Farooq",String.valueOf(ypos));

            break;

            }
            return false;


        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


}

Answer 1

public boolean onTouchEvent(MotionEvent e)
        {
            int xpos=(int) e.getX();
            int ypos=(int) e.getY();
            switch (e.getAction())
            {
            case MotionEvent.ACTION_DOWN:
             Log.d("DEBUG", "On touch (down)" + String.valueOf(xpos) + String.valueOf(ypos));
            case MotionEvent.ACTION_UP:
            Log.d("DEBUG", "On touch (up)" + String.valueOf(xpos) + String.valueOf(ypos));
            case MotionEvent.ACTION_MOVE:
            Log.d("DEBUG", "On touch (move)" + String.valueOf(xpos) + String.valueOf(ypos));
            break;
        }
        return true;

    }

然后重写draw方法

 @Override
  public void draw(Canvas canvas) {
   super.draw(canvas);
   }

所以你试试

canvas.drawLine(startX, startY, stopX, stopY, paint);

要让一条直线向上尝试

canvas.drawLine(xpos, ypos, xpos, getHeight() , new Paint());

获取高度应该是你屏幕的高度（因为你画了一条直线）

为此，变量 xpos 和 ypos 应该对所有方法都可用，所以添加

int xpos,ypos = 0; 

到代码的顶部（但在类声明中）

要在圆圈之间绘制 a，您需要在触摸时获取第一个圆圈 x,y 的位置，然后使用它们设置 drawLine 方法，如下所示：

currentCircleXpos, lastCircleXpos = 0; //you would set these in the onDraw method when the circle get's drawn.
currentCircleYpos, lastCircleypos = 0;


canvas.drawLine(currentCircleXpos, currentCircleYpos, lastCircleXpos, lastCircleYpos , new Paint());

OnDraw() 方法-------

 for (int y = 0; y < rows; y++)
    {
        for (int x = 0; x < cols; x++)
        {
            canvas.drawCircle((x + 1) * xStep, (y + 1) * yStep, 20, pDot);
             currentCircleXpos = x;
              currentCircleYpos = y; //gets the circle that is being drawn's location
        if (y == 0)
        {
            //canvas.drawLine((x + 1) * xStep, yStep, (x + 1) * xStep, rows * yStep, pDot);
        }                   
    }

    //canvas.drawLine(xStep, (y + 1) * yStep, cols * xStep, (y + 1) * yStep, pDot);
}