Android如何用手指画出流畅的线条
Som*_*omk 67 java android interpolation curve-fitting touch
http://marakana.com/tutorials/android/2d-graphics-example.html
我在下面使用这个例子.但当我在屏幕上移动我的手指太快时,线条会变成单个点.
我不确定我是否可以加快绘图速度.或者我应该用直线连接最后两个点.这两个解决方案中的第二个似乎是一个不错的选择,除非你的手指移动非常快,你将有一条直线的长段然后是尖锐的曲线.
如果有任何其他解决方案,听到它们会很棒.
在此先感谢您的帮助.
Joh*_*sen 108
如上所述,一个简单的解决方案是简单地用直线连接点.这是执行此操作的代码:
public void onDraw(Canvas canvas) {
Path path = new Path();
boolean first = true;
for(Point point : points){
if(first){
first = false;
path.moveTo(point.x, point.y);
}
else{
path.lineTo(point.x, point.y);
}
}
canvas.drawPath(path, paint);
}
确保你将油漆从填充变为中风:
paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(2);
paint.setColor(Color.WHITE);
另一种选择是使用quadTo方法将点连接到iterpolation:
public void onDraw(Canvas canvas) {
Path path = new Path();
boolean first = true;
for(int i = 0; i < points.size(); i += 2){
Point point = points.get(i);
if(first){
first = false;
path.moveTo(point.x, point.y);
}
else if(i < points.size() - 1){
Point next = points.get(i + 1);
path.quadTo(point.x, point.y, next.x, next.y);
}
else{
path.lineTo(point.x, point.y);
}
}
canvas.drawPath(path, paint);
}
这仍然会产生一些尖锐的边缘.
如果你真的雄心勃勃,你可以开始计算三次样条曲线,如下所示:
public void onDraw(Canvas canvas) {
Path path = new Path();
if(points.size() > 1){
for(int i = points.size() - 2; i < points.size(); i++){
if(i >= 0){
Point point = points.get(i);
if(i == 0){
Point next = points.get(i + 1);
point.dx = ((next.x - point.x) / 3);
point.dy = ((next.y - point.y) / 3);
}
else if(i == points.size() - 1){
Point prev = points.get(i - 1);
point.dx = ((point.x - prev.x) / 3);
point.dy = ((point.y - prev.y) / 3);
}
else{
Point next = points.get(i + 1);
Point prev = points.get(i - 1);
point.dx = ((next.x - prev.x) / 3);
point.dy = ((next.y - prev.y) / 3);
}
}
}
}
boolean first = true;
for(int i = 0; i < points.size(); i++){
Point point = points.get(i);
if(first){
first = false;
path.moveTo(point.x, point.y);
}
else{
Point prev = points.get(i - 1);
path.cubicTo(prev.x + prev.dx, prev.y + prev.dy, point.x - point.dx, point.y - point.dy, point.x, point.y);
}
}
canvas.drawPath(path, paint);
}
此外,我发现您需要更改以下内容以避免重复的动作事件:
public boolean onTouch(View view, MotionEvent event) {
if(event.getAction() != MotionEvent.ACTION_UP){
Point point = new Point();
point.x = event.getX();
point.y = event.getY();
points.add(point);
invalidate();
Log.d(TAG, "point: " + point);
return true;
}
return super.onTouchEvent(event);
}
并将dx和dy值添加到Point类:
class Point {
float x, y;
float dx, dy;
@Override
public String toString() {
return x + ", " + y;
}
}
这会产生平滑的线条,但有时必须使用循环连接点.此外,对于长绘图会话,这在计算上变得计算密集.
希望有助于...有趣的东西可以玩.
编辑
我汇总了一个展示这些不同技术的快速项目,包括Square的suggessted签名实现.享受:https://github.com/johncarl81/androiddraw
- 这是一篇关于这个主题的有趣文章.看起来像android批处理触摸事件:http://corner.squareup.com/2010/07/smooth-signatures.html (11认同)
- 第一个循环cubicTo()示例似乎是错误的.它应该遍历所有点,而不仅仅是最后一点. (3认同)
- @johncarl我同意Eric的观点.我认为曲线代码是错误的 - 第一个循环只能平滑最后几个点.我建议第一个循环从0开始,而不是从"points.size() - 2"开始.(这是基于我实际上将此代码复制到我的图形应用程序并进行测试的事实) (3认同)
- Android已经有一个内置功能,与此功能相同,功能更多,w/c你可以参考[这里](http://android-coding.blogspot.com/2014/05/composepatheffect-example.html) .只需使用johncarl的第一个例子,就可以实现平滑的边缘线. (3认同)
cai*_*ci2 34
这对你来说可能不再那么重要了,但我努力解决它并且我想分享,可能对其他人有用.
提供@johncarl解决方案的教程非常适合绘图,但它们为我的目的提供了限制.如果您将手指从屏幕上移开并将其放回,此解决方案将在最后一次点击和新点击之间画一条线,使整个图形始终连接.所以我试图找到一个解决方案,最后我得到了它!(对不起,如果听起来很明显,我是图形的初学者)
public class MainActivity extends Activity {
DrawView drawView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set full screen view
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
requestWindowFeature(Window.FEATURE_NO_TITLE);
drawView = new DrawView(this);
setContentView(drawView);
drawView.requestFocus();
}
}
public class DrawingPanel extends View implements OnTouchListener {
private static final String TAG = "DrawView";
private static final float MINP = 0.25f;
private static final float MAXP = 0.75f;
private Canvas mCanvas;
private Path mPath;
private Paint mPaint;
private LinkedList<Path> paths = new LinkedList<Path>();
public DrawingPanel(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
this.setOnTouchListener(this);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(6);
mCanvas = new Canvas();
mPath = new Path();
paths.add(mPath);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
for (Path p : paths){
canvas.drawPath(p, mPaint);
}
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
mX = x;
mY = y;
}
}
private void touch_up() {
mPath.lineTo(mX, mY);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath = new Path();
paths.add(mPath);
}
@Override
public boolean onTouch(View arg0, MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
}
我用你的手指画了android样本并稍微修改它来存储每个路径而不是最后一个路径!希望它可以帮到某人!
干杯.
Eri*_*ner 19
我已经尝试了几种方法来渲染运动事件的累积点.最后,通过计算两点之间的中点并将列表中的点作为二次贝塞尔曲线的锚点(除了通过简单线连接到下一个中点的第一个和最后一个点之外),我得到了最好的结果. ).
这样可以提供没有任何角落的平滑曲线.绘制的路径不会触及列表中的实际点,而是遍历每个中点.
Path path = new Path();
if (points.size() > 1) {
Point prevPoint = null;
for (int i = 0; i < points.size(); i++) {
Point point = points.get(i);
if (i == 0) {
path.moveTo(point.x, point.y);
} else {
float midX = (prevPoint.x + point.x) / 2;
float midY = (prevPoint.y + point.y) / 2;
if (i == 1) {
path.lineTo(midX, midY);
} else {
path.quadTo(prevPoint.x, prevPoint.y, midX, midY);
}
}
prevPoint = point;
}
path.lineTo(prevPoint.x, prevPoint.y);
}
如果您想简单：
public class DrawByFingerCanvas extends View {
private Paint brush = new Paint(Paint.ANTI_ALIAS_FLAG);
private Path path = new Path();
public DrawByFingerCanvas(Context context) {
super(context);
brush.setStyle(Paint.Style.STROKE);
brush.setStrokeWidth(5);
}
@Override
protected void onDraw(Canvas c) {
c.drawPath(path, brush);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
path.moveTo(x,y);
break;
case MotionEvent.ACTION_MOVE:
path.lineTo(x, y);
break;
default:
return false;
}
invalidate();
return true;
}
}
在活动中：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new DrawByFingerCanvas(this));
}
结果：
要删除所有图形，只需旋转屏幕。
我有非常类似的问题。调用onTouch方法时，还应该使用方法（在onTouch（MotionEvent事件）内部）
event.getHistorySize();
像这样
int histPointsAmount = event.getHistorySize();
for(int i = 0; i < histPointsAmount; i++){
// get points from event.getHistoricalX(i);
// event.getHistoricalY(i); and use them for your purpouse
}