Question

我扩展了View以使用canvas。我在onDraw（）方法中绘制基本绘图，当用户在画布中触摸时我必须在那里绘制图像，因为我在onTouchEvent（）方法中使用了canvas，它没有在那里绘制任何东西，代码如下，问题是什么？如何解决这个问题

public class ScreenView extends View(){

  static Canvas canvas;
    Bitmap bm;

    protected void onDraw(final Canvas canvas) {
        super.onDraw(canvas);
        this.canvas = canvas;
        bm = BitmapFactory.decodeResource(getResources(),
                R.drawable.ic_launcher);

        canvas.draw.......
        ......
        ...........


    }
    public boolean onTouchEvent(final MotionEvent event) {

        handleTouches(event.getX(), event.getY());

        return false;
    }
    public void handleTouches(float x, float y) {
        xLocTouch = (int) x;
        yLocTouched = (int) y;
        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        canvas.drawBitmap(bm, xLocTouch ,yLocTouched , paint);
    }
}

Answer 1

您应该在invalidate()内调用onTouchEvent方法，然后调用onDraw()方法，并且您应该存储x和y坐标，然后将位图绘制到此坐标，如下所示：

public class ScreenView extends View {
    int xLocTouched;
    int yLocTouched;
    Bitmap bm;

    protected void onDraw(final Canvas canvas) {
        super.onDraw(canvas);
        bm = BitmapFactory.decodeResource(getResources(),
                R.drawable.ic_launcher);

        //your basic drawings also should depends on xLocTouched and yLocTouched.

        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        canvas.drawBitmap(bm, xLocTouched ,yLocTouched , paint);

    }

    public boolean onTouchEvent(final MotionEvent event) {
        xLocTouched = (int) event.getX();
        yLocTouched = (int) event.getY();

        invalidate();

        return false;
    }
}

画布不在另一种方法中绘制图像

1 个答案: