我正在android studios上编写一个寻路代码，我正在使用一个名为drawsurface的视图类。这个类是在activity\u main.xml中使用的。我被困在如何生成细胞，我也有麻烦与ontouch方法。我有两个图像，一个是起点，另一个是终点。有了这个，我必须能够把起点放在任何单元格里，然后把终点放在任何单元格里。一旦发生这种情况，a*代码将生成一条最便宜的路径。然后可以接触任何其他不同的细胞，这将清除细胞除了新的起点，然后程序重新开始。下面是我的drawsurfce类，它包含所有loadnewmap，代码用于创建单元格集、启动单元格集阻止程序、计算屏幕上的单元格数和连接单元格。也不确定我的ondraw是否正确。现在如果我运行的程序，它是一个白色的屏幕，底部有一个信用按钮，我可以触摸屏幕，但它只把开始点放在屏幕上。
深色表面

package edu.fullsail.mgems.cse.pather.allisonhix;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PointF;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;

import java.util.ArrayList;

public class DrawSurface extends SurfaceView implements SurfaceHolder.Callback, View.OnTouchListener {

protected Bitmap mBMPStart = BitmapFactory.decodeResource(getResources(), R.drawable.start);
protected Bitmap mBMPEnd = BitmapFactory.decodeResource(getResources(), R.id.end);
protected ArrayList<PointF> mCellStart;
protected ArrayList<PointF> mCellEnd;
protected ArrayList<NavCell> mNavCell;

private int mCellCols;
private int mCellRows;
Rect mScreenDim = new Rect();
public NavCell[][] mCells;
static float CELL_SIZE = 64;
private SurfaceHolder mHolder;
private Object Canvas;
private Object PointF;
private Canvas canvas;

public DrawSurface(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
}

public void init() {
    getHolder().addCallback(this);
    setOnTouchListener(this);
    mBMPEnd = BitmapFactory.decodeResource(getResources(), R.drawable.end);
    mBMPStart = BitmapFactory.decodeResource(getResources(), R.drawable.start);
    setWillNotDraw(false);
    mCellStart = new ArrayList<>();
    mCellEnd = new ArrayList<>();
    View viewById = findViewById(R.id.dsField);
}

@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
    mHolder = surfaceHolder;
    Canvas c = mHolder.lockCanvas();
    if (c != null) mScreenDim.set(0, 0, c.getWidth(), c.getHeight());

    mHolder.unlockCanvasAndPost(c);

    loadNewMap();
    invalidate();
}

public void loadNewMap() {

    //calculate number of cells based on screen
    for (int i = 0; i < mCellCols; i++) {
        for (int j = 0; j < mCellRows; j++) {
            mCellCols = (int) Math.ceil((float) mScreenDim.width() / (float) CELL_SIZE);
            mCellRows = (int) Math.ceil((float) mScreenDim.height() / (float) CELL_SIZE);
        }
    }
    // create cells
    mCells = new NavCell[mCellRows][mCellCols];
    for (int j = 0; j < mCellRows; j++) {
        for (int i = 0; i < mCellCols; i++) {
            mCells[j][i] = new NavCell(i, j);
            mCells[j][i].setBounds(
                    i * CELL_SIZE,
                    j * CELL_SIZE,
                    (i * CELL_SIZE) + CELL_SIZE,
                    (j * CELL_SIZE) + CELL_SIZE);
        }
    }
    // set start cell
    mCellStart = mCells[mCellRows / 4][mCellCols / 2];
    mCellEnd = null;
    //set blockers
    int midRow = mCellRows / 2;
    {
        for (int j = 0; j < mCellRows; j++) {
            for (int i = 0; i < mCellCols; i++) {
                if (j == midRow && i > 0 && i < mCellCols - 1)
                    mCells[j][i].setImpassable();
            }
        }
    }
    // connect cells
    for (int j = 0; j < mCellRows; j++) {
        for (int i = 0; i < mCellCols; i++) {
            if (i > 0 && mCells[j][i - 1].isPassable())
                mCells[j][i].setNeighbor(0, mCells[j][i - 1]);
            if (j > 0 && mCells[j - 1][i].isPassable())
                mCells[j][i].setNeighbor(1, mCells[j - 1][i]);
            if (i < mCellCols - 1 && mCells[j][i + 1].isPassable())
                mCells[j][i].setNeighbor(2, mCells[j][i + 1]);
            if (j < mCellRows - 1 && mCells[j + 1][i].isPassable())
                mCells[j][i].setNeighbor(3, mCells[j + 1][i]);
        }
    }
}

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if (mCellEnd != null) {
        for (PointF end : mCellEnd) {
            canvas.drawBitmap(mBMPEnd, new Rect(0, 0, mBMPEnd.getWidth(), mBMPEnd.getHeight()),
                    new RectF(end.x - mBMPEnd.getWidth() / 2, end.y - mBMPEnd.getHeight() / 2,
                            end.x + mBMPEnd.getWidth() / 2, end.y + mBMPEnd.getHeight() / 2), new Paint());
        }
        if (mBMPStart != null) {
            for (PointF start : mCellStart) {
                canvas.drawBitmap(mBMPStart, new Rect(0, 0, mBMPStart.getWidth(), mBMPStart.getHeight()),
                        new RectF(start.x - mBMPStart.getWidth() / 2, start.y - mBMPStart.getHeight() / 2,
                                start.x + mBMPStart.getWidth() / 2, start.y + mBMPStart.getHeight() / 2), new Paint());
            }
        }

    }
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {

}

public boolean onTouch(android.view.View v, MotionEvent event) {
    if (event.getAction() == MotionEvent.ACTION_DOWN) {
        PointF start = new PointF(event.getX(), event.getY());
        mCellStart.add(start);
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            PointF end = new PointF(event.getX(), event.getY());
            mCellEnd.add(end);
        }
        invalidate();
    }
    return true;
}
}