如何使用View的子级制作绘图动画,逐条绘制每条路径的线条?
使用我在this StackOverflow answer中找到的代码,我可以成功地用手指在画布上绘制任何东西,并且我将在绘制它的同时看到我画的是什么。在此基础上,我想创建一个在按下按钮时触发的函数,该函数将做两件事:
- 擦除画布上绘制的内容。
- 通过以恒定的速度逐条重新绘制每条路径的线条,重播在清除画布之前在其上绘制的任何图片。
为此,我稍微修改了onTouchEvent
代码,使其相应地存储每个绘制的点:
@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(至少这是这样的想法)。问题是我不确定如何在画布上为每一行触发重绘。我尝试按如下方式存储";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划的按钮创建此方法:
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,replayStrokes
方法的行为不符合预期。这就像它仍然在思考和处理,当你最意想不到的时候,它会一下子刷新所有的变化;相反,我希望它是一个流畅的动画,你可以看到以前用手指绘制的整个路径,逐行、逐点地重播。我做错了什么?我应该更改哪些内容才能获得预期的行为?
解决方案
多亏了@VitorHugoSchwaab的评论,我终于想出了一个解决方案。提醒一下:我在这个问题中发布的所有代码都应该在public class DrawCanvas extends View
类中。也就是说:
因此,我将触发器方法&Quot;保留如下:
private int s, p;
private boolean replay_mode;
public void replayStrokes() {
s = 0;
p = 0;
replay_mode = true;
invalidate();
}
我像这样修改了onDraw
方法(我将其转换为Megamoth,但我可以稍后修复:p):
@Override
protected void onDraw(Canvas canvas) {
if (replay_mode) {
if (s == 0 && p == 0) {
Log.i("SANDBOX_INFO", "Replay Mode START");
canvas.drawRGB(255, 255, 255);
p++;
replayPath.reset();
replayPath.moveTo(strokes.get(0).points.get(0).x,
strokes.get(0).points.get(0).y);
invalidate();
} else {
Log.i("SANDBOX_INFO", "Replaying --> S:" + s + " P:" + p);
if (p == 0) {
replayPath.moveTo(strokes.get(s).points.get(p).x,
strokes.get(s).points.get(p).y);
} else {
replayPath.lineTo(strokes.get(s).points.get(p).x,
strokes.get(s).points.get(p).y);
canvas.drawPath(replayPath, mPaint);
}
int points_size = strokes.get(s).points.size();
if (s == strokes.size() - 1 && p == points_size - 1) {
Log.i("SANDBOX_INFO", "Replay Mode END");
replay_mode = false;
}
else if (p == points_size - 1) {
s++;
p = 0;
} else {
p++;
}
}
invalidate();
} else {
canvas.drawPath(mPath, mPaint);
}
super.onDraw(canvas);
}
这是可行的。但是,在重播笔划时,会出现闪烁的毛刺效果。我认为这可能是因为它实际上是在每一帧上重新绘制整个重放路径。基于此猜测,当我有更多时间编写代码时,我将尝试解决此问题。
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