Question

我有画布我正在绘制位图。我将画布和位图的尺寸设置为变量并打印出它们各自的值。当我尝试绘制位图时，它不显示。

SurfaceView代码：

protected void onDraw(Canvas canvas) {
    if (canvas != null) {
        canvas.drawColor(Color.WHITE);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setFilterBitmap(true);
        paint.setDither(true);
        int canvasWidth = canvas.getWidth();
        int canvasHeight = canvas.getHeight();
        int memoryManiaWidth = memoryMania.getWidth();
        int memoryManiaHeight = memoryMania.getHeight();
        Rect src = new Rect(0,0,memoryManiaWidth,memoryManiaHeight);
        Rect dst = new Rect(0,0,canvasWidth,canvasWidth*(memoryManiaHeight/memoryManiaWidth));
        Log.d("MM","CW"+ String.valueOf(canvasWidth));
        Log.d("MM","MMH" + String.valueOf((memoryManiaHeight)));
        Log.d("MM","MMW" + String.valueOf((memoryManiaWidth)));
        Log.d("MM",String.valueOf(canvasWidth*(memoryManiaHeight/memoryManiaWidth)));
        canvas.drawBitmap(memoryMania,src,dst,paint);
    }

}

Logcat输出：

06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ CW1080
06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ MMH419
06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ MMW951
06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ 0

如果我将dst Rect变量的bottom参数更改为除当前值之外的任何值，则显示位图。例如，如果我改变了

dst = new Rect(.....,canvasWidth*(......));

到

dst = new Rect(.....,canvasWidth));

它会显示。

正如你在logcat输出中看到的那样，

canvasWidth*(memoryManiaHeight/memoryManiaWidth)

被评估为0.为什么会发生这种情况，我该怎么做才能解决它？

Answer 1

从此处更改您的计算：

canvasWidth*(memoryManiaHeight/memoryManiaWidth)

到此：

(canvasWidth*memoryManiaHeight)/memoryManiaWidth

如果先评估(memoryManiaHeight/memoryManiaWidth)，那么由于整数除法，它将评估为零。

Answer 2

memoryManiaHeight的价值是否有可能小于memoryManiaWidth？它们都是整数，因此产生零。尝试检查两个变量的值。这应该有效：

(int) ( canvasWidth * ((float)memoryManiaHeight/memoryManiaWidth) );

位图没有显示在画布上

2 个答案: