Android应用程序上未显示自定义可绘制视图

我目前正在构建一个Android应用程序，它根据难度设置生成一个迷宫，轻松生成一个5x5的迷宫，有边框，中等8x8，硬11x11。迷宫由黑色方块组成，这些方块的位置构成了一条从左上到右下的路径，以及迷宫周围的一个正方形边界。如果有一个黑色的正方形，你不能朝那个方向移动，等等。。。目前，只有界面正在构建中，没有任何用户交互，我将在稍后添加。代码也有点混乱-我知道这一点，并将在问题解决后进行整理

问题是迷宫没有显示——只是一个空白！我使用一个XML文件和活动作为主界面，并使用一个自定义视图作为迷宫的可绘制视图

这是在游戏中创建界面的活动/类。这里使用的Level类保存有关当前分数/迷宫/用户位置等的数据。它已经过测试，我非常相信它能工作

public class InGameInterface extends Activity {

    Level level;;
    MazeView maze;

    private boolean[][] currentMaze = null;

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

        level = new Level();

        currentMaze = level.getNewMaze();
        loadMazeDisplay();
    }   

    private void loadMazeDisplay()
    {
        maze = new MazeView(this, level, currentMaze);

        RelativeLayout mazeHolder = (RelativeLayout) findViewById(R.id.maze);
        LayoutParams lP = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

        mazeHolder.addView(maze, lP);
    }
}

---

下面是我试图插入自定义视图的XML文件的相关部分。我想说的是，忘记宽度像素和高度像素，因为它们取决于布局。要使用它们，您必须按照可能需要的度量来实现。但是，由于视图非常简单，只需使用canvas.getWidth和getHeight中的值即可。试试下面的方法，看看是否有效

private static final int CELLS_PER_SCREEN = 5; // the number of cells that fit on a view

protected void onDraw(Canvas canvas) {

    int totalWidth=canvas.getWidth(), 
        totalHeight=canvas.getHeight(), 
        cellWidthInPixels=totalWidth / CELLS_PER_SCREEN,
        cellHeightInPixels=totalHeight / CELLS_PER_SCREEN;

    canvas.drawRect(0, 0, totalWidth, totalHeight, background);

    for (int counterX = 0, xlen=level.getWidth(); counterX < xlen; counterX++) {
        for (int counterY = 0, ylen=level.getHeight(); counterY < ylen; counterY++) {
            if (!mazeIsPath[counterX][counterY]) {
                canvas.drawRect(
                     (float)(cellWidthInPixels * counterX), 
                     (float)(cellHeightInPixels * counterX), 
                     (float)(cellWidthInPixels * (counterX + 1)), 
                     (float)(cellHeightInPixels * (counterY + 1)), cell
                );
            }
        }
    }

    canvas.drawCircle( (float)((cellWidthInPixels * level.getCurrentX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getCurrentX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (2f/3f)), ball);
    canvas.drawCircle( (float)((cellWidthInPixels * level.getFinalX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getFinalX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (4f/5f)), target);

    Log.w("onDraw width", widthInPixels.toString());
    Log.w("onDraw height", heightInPixels.toString());
    Integer cWidth = new Integer(canvas.getWidth());
    Integer cHeight = new Integer(canvas.getHeight());
    Log.w("canvas width", cWidth.toString());
    Log.w("cavas height", cHeight.toString());
}

还有一些关于onDraw的建议：onDraw调用非常频繁，尽可能优化非常重要

使用int而不是Integer，Integer是一个对象，而int只是一个快速的基本类型。 预先计算易于重用的内容，特别是浮点乘法。你的画圈做了很多数学运算，只会随着cellWidthInPixels的变化而变化。。。所以，只要计算一次，每次cellWidthInPixels改变

---

只是一个简单的猜测。。。在onDraw vs canvas.getWidth和canvas.getHeight中打印heightinpixels、widthinpixels的值。。而且你说的这个白色，是第一个drawrect的背景吗？而且你在哪里初始化cellwidthinpixels？谢谢你的回复-我试着把背景改成灰色，但还是没有显示出来！此外，widthInpixels和heightInPixels均为0，画布宽度为739，画布高度为670。我如上所述修改了onDraw方法上的代码，但没有任何效果-仍然没有显示任何内容！我得说你是个传奇人物D非常感谢你，它现在起作用了——我花了两天时间才弄明白。。。

public class MazeView extends View
{
private Activity context;
private Level level;
private boolean mazeIsPath[][] = null;

private Integer widthInPixels = 0, heightInPixels = 0;
private Integer cellWidthInPixels = 0, cellHeightInPixels = 0;
private Paint cell, ball, background, target;

public MazeView(Context context, Level level, boolean[][] maze) 
{
    super(context);
    this.context = (Activity) context;
    this.level = level;
    mazeIsPath = maze;

    cell = new Paint();
    cell.setColor(getResources().getColor(R.color.textColor));

    ball = new Paint();
    ball.setColor(getResources().getColor(R.color.splashBackground));

    background = new Paint();
    background.setColor(getResources().getColor(R.color.gameInterfaceBackground));

    target = new Paint();
    target.setColor(getResources().getColor(R.color.buttonBackground));

    widthInPixels = this.getWidth();
    heightInPixels = this.getHeight();

    setFocusable(true);
    this.setFocusableInTouchMode(true);
}

protected void onSizeChanged(Integer newW, Integer newH, Integer oldW, Integer oldH)
{
    widthInPixels = newW;
    heightInPixels = newH;

    super.onSizeChanged(newW, newH, oldW, oldH);
}

protected void onDraw(Canvas canvas)
{
    Integer counterX = 0, counterY = 0;

    canvas.drawRect(0, 0, widthInPixels, heightInPixels, background);

    for(counterX = 0; counterX < level.getWidth(); counterX++)
    {
        for(counterY = 0; counterY < level.getHeight(); counterY++)
        {
            if(mazeIsPath[counterX][counterY] != true)
            {
                canvas.drawRect((float)(cellWidthInPixels * counterX), (float)(cellHeightInPixels * counterX), (float)(cellWidthInPixels * (counterX + 1)), (float)(cellHeightInPixels * (counterY + 1)), cell);
            }
        }
    }

    canvas.drawCircle( (float)((cellWidthInPixels * level.getCurrentX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getCurrentX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (2f/3f)), ball);
    canvas.drawCircle( (float)((cellWidthInPixels * level.getFinalX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getFinalX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (4f/5f)), target);
}
}

protected void onDraw(Canvas canvas)
{
    Integer counterX = 0, counterY = 0;
    widthInPixels = new Integer(canvas.getWidth());
    heightInPixels = new Integer(canvas.getHeight());

    canvas.drawRect(0, 0, widthInPixels, heightInPixels, background);

    for(counterX = 0; counterX < level.getWidth(); counterX++)
    {
        for(counterY = 0; counterY < level.getHeight(); counterY++)
        {
            if(mazeIsPath[counterX][counterY] != true)
            {
                canvas.drawRect((float)(cellWidthInPixels * counterX), (float)(cellHeightInPixels * counterX), (float)(cellWidthInPixels * (counterX + 1)), (float)(cellHeightInPixels * (counterY + 1)), cell);
            }
        }
    }

    canvas.drawCircle( (float)((cellWidthInPixels * level.getCurrentX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getCurrentX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (2f/3f)), ball);
    canvas.drawCircle( (float)((cellWidthInPixels * level.getFinalX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getFinalX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (4f/5f)), target);

    Log.w("onDraw width", widthInPixels.toString());
    Log.w("onDraw height", heightInPixels.toString());
    Integer cWidth = new Integer(canvas.getWidth());
    Integer cHeight = new Integer(canvas.getHeight());
    Log.w("canvas width", cWidth.toString());
    Log.w("cavas height", cHeight.toString());
}

private static final int CELLS_PER_SCREEN = 5; // the number of cells that fit on a view

protected void onDraw(Canvas canvas) {

    int totalWidth=canvas.getWidth(), 
        totalHeight=canvas.getHeight(), 
        cellWidthInPixels=totalWidth / CELLS_PER_SCREEN,
        cellHeightInPixels=totalHeight / CELLS_PER_SCREEN;

    canvas.drawRect(0, 0, totalWidth, totalHeight, background);

    for (int counterX = 0, xlen=level.getWidth(); counterX < xlen; counterX++) {
        for (int counterY = 0, ylen=level.getHeight(); counterY < ylen; counterY++) {
            if (!mazeIsPath[counterX][counterY]) {
                canvas.drawRect(
                     (float)(cellWidthInPixels * counterX), 
                     (float)(cellHeightInPixels * counterX), 
                     (float)(cellWidthInPixels * (counterX + 1)), 
                     (float)(cellHeightInPixels * (counterY + 1)), cell
                );
            }
        }
    }

    canvas.drawCircle( (float)((cellWidthInPixels * level.getCurrentX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getCurrentX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (2f/3f)), ball);
    canvas.drawCircle( (float)((cellWidthInPixels * level.getFinalX()) + (0.5f*(cellWidthInPixels))), (float)((cellHeightInPixels * level.getFinalX()) + (0.5f*(cellHeightInPixels))), (float)(cellHeightInPixels * (4f/5f)), target);

    Log.w("onDraw width", widthInPixels.toString());
    Log.w("onDraw height", heightInPixels.toString());
    Integer cWidth = new Integer(canvas.getWidth());
    Integer cHeight = new Integer(canvas.getHeight());
    Log.w("canvas width", cWidth.toString());
    Log.w("cavas height", cHeight.toString());
}