使用我在中找到的代码这个 StackOverflow 答案 https://stackoverflow.com/a/61843394/3692177我成功地可以用手指在画布上绘制任何内容,并且在绘制时我会看到我绘制的内容。由此,我想创建一个在按下按钮时触发的函数,该函数将执行两件事:
- 擦除画布上绘制的内容。
- 通过以恒定的速度一条一条地重新绘制每条路径的线条,重播在画布被清除之前在其上绘制的所有图片。
为此,我稍微修改了onTouchEvent
代码,因此它相应地存储每个绘制点:
@Override
public boolean onTouchEvent(MotionEvent event) {
StrokePoint point;
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
mPath.moveTo(event.getX(), event.getY());
// Retrieve strokes in memory
stroke_buffer = new Stroke();
stroke_buffer.points = new ArrayList<StrokePoint>();
point = new StrokePoint();
point.x = event.getX();
point.y = event.getY();
stroke_buffer.points.add( point );
break;
case MotionEvent.ACTION_MOVE:
mPath.lineTo(event.getX(), event.getY());
// Retrieve strokes in memory
point = new StrokePoint();
point.x = event.getX();
point.y = event.getY();
stroke_buffer.points.add( point );
invalidate();
break;
case MotionEvent.ACTION_UP:
// Retrieve strokes in memory
strokes.add(stroke_buffer);
break;
default:
break;
}
return true;
}
这样,我可以稍后在循环中加载 X 和 Y 点(至少是这个想法)。问题是我不确定如何触发画布上每行的“重绘”。我尝试像这样存储“onDraw”中的画布:
@Override
protected void onDraw(Canvas canvas) {
canvas.drawPath(mPath, mPaint);
// For trying to make the "redraw" later
this.mCanvas = canvas;
super.onDraw(canvas);
}
然后,我为要擦除并重播先前绘制的笔画的按钮创建此方法:
public void replayStrokes() {
// I start a new path from scratch ad-hoc the "redraw" animation.
mPath = new Path();
Log.i("SANDBOX_INFO", "Button pressed");
// Intention here is leaving the "whiteboard" clear again.
mCanvas.drawRGB(255, 255, 255);
invalidate();
this.draw(mCanvas);
SystemClock.sleep(1000);
// Redraw "line by line" loop
mPath.moveTo(strokes.get(0).points.get(0).x,
strokes.get(0).points.get(0).y);
for (int i = 0; i < strokes.size(); i++) {
for (int j = 0; j < strokes.get(i).points.size(); j++) {
if (i == 0 && j == 0) continue;
mPath.lineTo(strokes.get(i).points.get(j).x,
strokes.get(i).points.get(j).y);
mCanvas.drawPath(mPath, mPaint);
invalidate();
this.draw(mCanvas);
SystemClock.sleep(100);
}
}
}
当我按下按钮时,该方法replayStrokes
行为不符合预期。就好像它仍然在“思考”(处理),并且在你最意想不到的时候,一击刷新了所有的变化;相反,我希望它是一个平滑的动画,您可以看到之前用手指绘制的整个路径,逐行、逐点地重播。我究竟做错了什么?我应该改变什么才能获得预期的行为?