如何在带有动画的 Android 画布上绘制路径？
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时间：2020-08-20 09:33:27 来源:igfitidea点击:
How to draw a path on an Android canvas with animation?
提问by Romain Piel
I'm making an Android app and I've got a tricky thing to do. I need to draw a path on a canvas but the drawing should be animated (ie. drawing point after point with a slight delay).
我正在制作一个 Android 应用程序，但我有一件棘手的事情要做。我需要在画布上绘制一条路径，但绘图应该是动画的（即一点点延迟绘制）。
Is it possible to make something like this using Android SDK? If not, how could I produce this effect?
是否可以使用 Android SDK 制作这样的东西？如果没有，我怎么能产生这种效果？
回答by Hesham Saeed
Try this code, I used it to draw a heartbeat using Path& Canvas:
试试这个代码，我用它来使用Path&绘制心跳Canvas：
public class TestActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new HeartbeatView(this));
}
public static class HeartbeatView extends View {
private static Paint paint;
private int screenW, screenH;
private float X, Y;
private Path path;
private float initialScreenW;
private float initialX, plusX;
private float TX;
private boolean translate;
private int flash;
private Context context;
public HeartbeatView(Context context) {
super(context);
this.context=context;
paint = new Paint();
paint.setColor(Color.argb(0xff, 0x99, 0x00, 0x00));
paint.setStrokeWidth(10);
paint.setAntiAlias(true);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStyle(Paint.Style.STROKE);
paint.setShadowLayer(7, 0, 0, Color.RED);
path= new Path();
TX=0;
translate=false;
flash=0;
}
@Override
public void onSizeChanged (int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
screenW = w;
screenH = h;
X = 0;
Y = (screenH/2)+(screenH/4)+(screenH/10);
initialScreenW=screenW;
initialX=((screenW/2)+(screenW/4));
plusX=(screenW/24);
path.moveTo(X, Y);
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
//canvas.save();
flash+=1;
if(flash<10 || (flash>20 && flash<30))
{
paint.setStrokeWidth(16);
paint.setColor(Color.RED);
paint.setShadowLayer(12, 0, 0, Color.RED);
}
else
{
paint.setStrokeWidth(10);
paint.setColor(Color.argb(0xff, 0x99, 0x00, 0x00));
paint.setShadowLayer(7, 0, 0, Color.RED);
}
if(flash==100)
{
flash=0;
}
path.lineTo(X,Y);
canvas.translate(-TX, 0);
if(translate==true)
{
TX+=4;
}
if(X<initialX)
{
X+=8;
}
else
{
if(X<initialX+plusX)
{
X+=2;
Y-=8;
}
else
{
if(X<initialX+(plusX*2))
{
X+=2;
Y+=14;
}
else
{
if(X<initialX+(plusX*3))
{
X+=2;
Y-=12;
}
else
{
if(X<initialX+(plusX*4))
{
X+=2;
Y+=6;
}
else
{
if(X<initialScreenW)
{
X+=8;
}
else
{
translate=true;
initialX=initialX+initialScreenW;
}
}
}
}
}
}
canvas.drawPath(path, paint);
//canvas.restore();
invalidate();
}
}
}
It uses drawing a Path point by point with couple of effects using counters. You can take what you need and transfer it to SurfaceView which is more efficient.
它使用计数器逐点绘制路径，并具有多种效果。你可以把你需要的东西转移到更高效的 SurfaceView 上。
回答by Kazekage Gaara
I hope this is what you are looking for. It draws the path on user touch, you could simply tweek it to achieve what you desire.
我希望这就是你正在寻找的。它在用户触摸上绘制路径，你可以简单地调整它来实现你想要的。
public class MyCanvas extends Activity implements OnTouchListener{
DrawPanel dp;
private ArrayList<Path> pointsToDraw = new ArrayList<Path>();
private Paint mPaint;
Path path;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
dp = new DrawPanel(this);
dp.setOnTouchListener(this);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
requestWindowFeature(Window.FEATURE_NO_TITLE);
mPaint = new Paint();
mPaint.setDither(true);
mPaint.setColor(Color.WHITE);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(30);
FrameLayout fl = new FrameLayout(this);
fl.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
fl.addView(dp);
setContentView(fl);
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
dp.pause();
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
dp.resume();
}
public class DrawPanel extends SurfaceView implements Runnable{
Thread t = null;
SurfaceHolder holder;
boolean isItOk = false ;
public DrawPanel(Context context) {
super(context);
// TODO Auto-generated constructor stub
holder = getHolder();
}
@Override
public void run() {
// TODO Auto-generated method stub
while( isItOk == true){
if(!holder.getSurface().isValid()){
continue;
}
Canvas c = holder.lockCanvas();
c.drawARGB(255, 0, 0, 0);
onDraw(c);
holder.unlockCanvasAndPost(c);
}
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
synchronized(pointsToDraw)
{
for (Path path : pointsToDraw) {
canvas.drawPath(path, mPaint);
}
}
}
public void pause(){
isItOk = false;
while(true){
try{
t.join();
}catch(InterruptedException e){
e.printStackTrace();
}
break;
}
t = null;
}
public void resume(){
isItOk = true;
t = new Thread(this);
t.start();
}
}
@Override
public boolean onTouch(View v, MotionEvent me) {
// TODO Auto-generated method stub
synchronized(pointsToDraw)
{
if(me.getAction() == MotionEvent.ACTION_DOWN){
path = new Path();
path.moveTo(me.getX(), me.getY());
//path.lineTo(me.getX(), me.getY());
pointsToDraw.add(path);
}else if(me.getAction() == MotionEvent.ACTION_MOVE){
path.lineTo(me.getX(), me.getY());
}else if(me.getAction() == MotionEvent.ACTION_UP){
//path.lineTo(me.getX(), me.getY());
}
}
return true;
}
}
回答by Baffled
This might help... It draws adjacent circles instead of a path to simulate an animatable path.
这可能会有所帮助...它绘制相邻的圆圈而不是路径来模拟可动画路径。
public class PathAnimatable {
private final float CIRCLE_SIZE = 2.5f;
public float SPPED_SCALE = 1f;
private float steps = 0;
private float pathLength;
private PathMeasure pathMeasure;
private float totalStepsNeeded;
private float[] point = new float[]{0f, 0f};
private float stride;
public PathAnimatable() {
this(null);
}
public PathAnimatable(Path path) {
super(path);
init();
}
private void init() {
pathMeasure = new PathMeasure(path, false);
pathLength = pathMeasure.getLength();
stride = CIRCLE_SIZE * 0.5f;
totalStepsNeeded = pathLength / stride;
steps = 0;
}
@Override
public void setPath(Path path) {
super.setPath(path);
init();
}
// Called this from your locked canvas loop function
public void drawShape(Canvas canvas, Paint paint) {
if (steps <= pathLength) {
for (float i = 0; i < steps ; i += stride) {
pathMeasure.getPosTan(i, point, null);
canvas.drawCircle(point[0], point[1], CIRCLE_SIZE, paint);
}
steps += stride * SPPED_SCALE;
} else {
steps = 0;
}
}
}
