使用 onTouchEvent 保存绘制到 bitmap 上的图像

Question

我正在尝试触摸我的应用程序区域以在屏幕上放置一个与门。 因此，当我触摸与门区域，然后再次触摸以将其放置在电路上时，门会在我触摸的位置被绘制，但一旦我再次触摸，它就会消失。

我使用 canvas.drawBitmap 静态创建了一个电路，它们出现并停留在那里。 意思是，我创建了大量留在屏幕上的 canvas.drawBitmap 图像。

@Override
    public boolean onTouchEvent(MotionEvent motionEvent) {
        Log.d("Debugging", "In onTouchEvent");

        if((motionEvent.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_UP) {


            placeComponent();
            Touch.horizontalTouched = (int)motionEvent.getX()/ grid.getBlockSize();
            Touch.verticalTouched = (int)motionEvent.getY()/ grid.getBlockSize();
        }

        draw();
        return true;
    }

    void placeComponent(){
        Log.d("Debugging", "In placeComponent");

        // Convert the float screen coordinates
        // into int grid coordinates
        touchTemp = whatWasTouched(Touch.horizontalTouched, Touch.verticalTouched);
    }

    private void regionHit() {
        Bitmap _andTest = BitmapFactory.decodeResource(getResources(), R.drawable.andgatetrans);

        if(touchTemp.equals("AND")){
            canvas.drawBitmap(_andTest,Touch.horizontalTouched*grid.getBlockSize(),Touch.verticalTouched*grid.getBlockSize(),null);
            //drawIcons.drawANDGatev2(canvas,Touch.horizontalTouched*grid.getBlockSize(),Touch.verticalTouched*grid.getBlockSize());
        }
        if(touchTemp.equals("OR")){
        }
        if(touchTemp.equals("NOT")){
        }
        if(touchTemp.equals("SWITCH")){
        }

    }
    // used to tell regionHit() what to do
    private String whatWasTouched(float horizontalTouched, float verticalTouched) {
        if(horizontalTouched >= 5.0 && horizontalTouched <= 9.0){
            if(verticalTouched >= 0.0 && verticalTouched <=4.0){
                return "AND";
            }
        }
        if(horizontalTouched >= 5.0 && horizontalTouched <= 9.0){
            if(verticalTouched >= 5.0 && verticalTouched <=9.0){
                return "OR";
            }
        }
        if(horizontalTouched >= 5.0 && horizontalTouched <= 9.0){
            if(verticalTouched >= 10.0 && verticalTouched <=14.0){
                return "NOT";
            }
        }
        if(horizontalTouched >= 5.0 && horizontalTouched <= 9.0){
            if(verticalTouched >= 15.0 && verticalTouched <=19.0){
                return "SWITCH";
            }
        }
        if(horizontalTouched >= 0.0 && horizontalTouched <= 4.0){
            if(verticalTouched >= 0.0 && verticalTouched <=4.0){
                return "Play/Pause";
            }
        }
        if(horizontalTouched >= 0.0 && horizontalTouched <= 4.0){
            if(verticalTouched >= 5.0 && verticalTouched <=9.0){
                return "EDIT";
            }
        }
        if(horizontalTouched >= 0.0 && horizontalTouched <= 4.0){
            if(verticalTouched >= 10.0 && verticalTouched <=14.0){
                return "WIRE";
            }
        }
        if(horizontalTouched >= 0.0 && horizontalTouched <= 4.0){
            if(verticalTouched >= 15.0 && verticalTouched <=19.0){
                return "LED";
            }
        }

        return "-1";
    }

注意：在 onTouchEvent() 上方的 draw() 中调用了 regionTouched() 我希望能够触摸我的单屏应用程序中指示“与”门的区域，然后再次触摸以将其放置在canvas 并让它留在那里，并在放置它的 canvas 上分配其 position。 但是一旦我再次触摸屏幕，它的所有功能都会被放置和移除。

Answer 1

好的，因此使用 whatWasTouched() 方法选择了您的与门并放置在 canvas 的空白部分，重复您的与门消失并且您希望它停留在其 position？ 为此，您需要将与门的 position 保存在某处。

在您的 regionHit() 方法中，您正在绘制 AND 门 bitmap。

canvas.drawBitmap(_andTest,Touch.horizontalTouched*grid.getBlockSize(),Touch.verticalTouched*grid.getBlockSize(),null);

然后在下一个触摸事件中，您的 whatWasTouched() 可能不会返回 AND 门，并且您的 Touch class 将具有更新的触摸点值。 这就是为什么您在下一次触摸中看不到 AND 门的原因。

因此，您需要将选定的门及其 position 保存在 canvas 上。

创建 class 门

public class Gate {

    private Bitmap bitmap;
    private int drawX;
    private int drawY;

    public Gate(Bitmap bitmap, int drawX, int drawY) {
        this.bitmap = bitmap;
        this.drawX = drawX;
        this.drawY = drawY;
    }

    public void draw(Canvas c) {
        c.drawBitmap(bitmap, drawX, drawY, null);
    }

    public void updateDrawPosition(int drawX, int drawY) {
        this.drawX = drawX;
        this.drawY = drawY;
    }

}

并像这样在您的视图中使用上面的 class

public class GatesView extends View {

    private ArrayList<Gate> gates;
    private Bitmap andGateBitmap;

    public GatesView(Context context) {
        super(context);
        // bitmap should be decoded here
        andGateBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.andgatetrans);

        final int initialCapacity = 5;
        gates = new ArrayList<>(initialCapacity);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // draw all saved gates in the list.
        final int listSize = gates.size();
        for (int i = 0; i < listSize; i++)
            gates.get(i).draw(canvas);

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        // when a new gate is selected add it to gatesList
        gates.add(new Gate(andGateBitmap, initial Xpos to draw, initial Ypos to draw)); // bitmap should not be decoded from Resource in onDraw() or onTouchEvent().
        invalidate(); // tell android that our view has updated and needs to be redrawn.
        return true;
    }
}