从 onTouchEvent function 获取 Android 中 SurfaceView 的像素

Question

How to get pixel of SurfaceView in Android

I want to extend the custom class of SurfaceView and override onTouchEvent

private fun getBitmap(): Bitmap {
    /*mSurfaceView!!.isDrawingCacheEnabled = true
    mSurfaceView!!.buildDrawingCache(true)
    val bitmap: Bitmap = Bitmap.createBitmap(mSurfaceView!!.drawingCache)
    // mSurfaceView!!.isDrawingCacheEnabled = false
    // mSurfaceView!!.destroyDrawingCache()*/
    val bitmap =
        Bitmap.createBitmap(
            mSurfaceView!!.width,
            mSurfaceView!!.height,
            Bitmap.Config.ARGB_8888
        )
    val canvas = Canvas(bitmap)
    mSurfaceView!!.draw(canvas)
    return bitmap
}

It always returns a black Bitmap

Answer 1

Hopefully I understood what you meant

class CustomSurfaceView(context: Context?, attrs: AttributeSet?) : SurfaceView(context, attrs) {

    override fun onTouchEvent(event: MotionEvent?): Boolean {

        var x = event?.getX();
        var y = event?.getY();

        Log.d("CustomSurfaceView", "Pixel($x, $y)");

        return super.onTouchEvent(event)
    }
}

EDIT

This code will save the last rendered bitmap, therefore allowing you to use the getPixel function.

class CustomSurfaceView(context: Context?, attrs: AttributeSet?) : SurfaceView(context, attrs) {

    var bitmap: Bitmap? = null;

    override fun onTouchEvent(event: MotionEvent?): Boolean {

        if(event != null) {

            val x = event?.x;
            val y = event?.y;

            if (bitmap != null) {
                val pixel = bitmap?.getPixel(x!!.toInt(), y!!.toInt());
                if (pixel != null)
                    Log.d("CustomSurfaceView", "rgb(${Color.red(pixel)}, ${Color.green(pixel)}, ${Color.blue(pixel)})");
            }
            Log.d("CustomSurfaceView", "Pixel($x, $y)");

        }
        return super.onTouchEvent(event)
    }

    override fun draw(canvas: Canvas?) {
        if(canvas != null) {
            val width = canvas.width;
            val height = canvas.height;
            bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
            if(bitmap != null)
                super.draw(Canvas(bitmap!!))
        }else {
            super.draw(canvas)
        }
    }
}

For the onDraw function to be called you need to add these line in your activity:

CustomSurfaceView surfaceView = findViewById(R.id.custom_surface_view);

surfaceView.setWillNotDraw(true);