我已经在这几天没有找到一个好的解决方案（至少对我而言）。
基本上我需要做的是绘制动画虚线曲线，这将代表基本游戏的导弹轨迹。该轨迹将接受起始，中间和最终x，y。我读了很多关于动画曲线甚至是直线的Q / A，但是与我必须做的相比，它们看起来非常复杂。
我有一个带有onclick侦听器的按钮，可触发导弹发射，但直到现在它只是绘制静态线而没有任何动画。
香蕉的轨迹没有画，但你明白了。
再次，从你的例子开始，我试图使用数组和for循环绘制同时曲线，但我得到的是有时，并非总是，应用程序崩溃与nullpointer异常，不知道为什么。我究竟做错了什么？这是我的代码：
public class DrawDottedCurve extends View {
Path[] path = new Path[8];
Path[] drawingPath = new Path[8];
PathMeasure[] measure = new PathMeasure[8];
Path[] segmentPath = new Path[8];
float[] length = new float[8];
float[] start = new float[8];
float[] percent = new float[8];
Paint paint = new Paint();
float x1;
float y1;
float x3;
float y3;
long k = 0;
Canvas canvas;
Random r = new Random();
public DrawDottedCurve(Context context, int a, int b, int c, int d) {
super(context);
x1 = a;
y1 = b;
x3 = c;
y3 = d;
paint.setAlpha(255);
paint.setStrokeWidth(2);
paint.setColor(Color.RED);
paint.setStyle(Style.STROKE);
paint.setPathEffect(new DashPathEffect(new float[] { 2, 4 }, 50));
for (int i = 0; i < 8; i++) {
k = r.nextInt(100 - 30) + 30;
path[i] = new Path();
path[i].moveTo(x1 + k, y1 + k); //
path[i].quadTo((x3 + k - x1 + k) / 2, (y3 + k - y1 + k) / 2,
x3 + k, y3 + k); // Calculate Bezier Curves
}
final long DRAW_TIME = 10000;
CountDownTimer timer = new CountDownTimer(DRAW_TIME, 100) {
@Override
public void onTick(long millisUntilFinished) {
Log.d("Timer", "Inizio");
for (int i = 0; i < 8; i++) {
start[i] = 0;
measure[i] = new PathMeasure();
measure[i].setPath(path[i], false);
percent[i] = ((float) (DRAW_TIME - millisUntilFinished))
/ (float) DRAW_TIME;
segmentPath[i] = new Path();
drawingPath[i] = new Path();
length[i] = measure[i].getLength() * percent[i];
measure[i].getSegment(start[i], length[i], segmentPath[i],
true);
start[i] = length[i];
drawingPath[i].addPath(segmentPath[i]);
}
invalidate();
;
}
@Override
public void onFinish() {
for (int i = 0; i < 8; i++) {
measure[i].getSegment(start[i], measure[i].getLength(),
segmentPath[i], true);
drawingPath[i].addPath(segmentPath[i]);
}
invalidate();
Log.d("Timer", "Fine");
}
};
timer.start();
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
for (int i = 0; i < 8; i++) {
canvas.drawPath(drawingPath[i], paint);
invalidate();
}
}
}
答案 0 :(得分：0)
假设您有要绘制的画布和要跟踪的路径，则此代码应该可以为其设置动画。
private void init() {
missilePath = new Path();
missileDrawPath = new Path();
mPaint = new Paint();
mPaint.setStrokeWidth(3);
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Style.STROKE);
mPaint.setAntiAlias(true);
PathEffect dashEffect = new DashPathEffect(new float[] {2, 4}, 0);
mPaint.setPathEffect(dashEffect);
final long DRAW_TIME = 5000;
timer = new CountDownTimer(DRAW_TIME, 100) {
PathMeasure measure = new PathMeasure();
Path segmentPath = new Path();
float start = 0;
@Override
public void onTick(long millisUntilFinished) {
measure.setPath(missilePath, false);
float percent = ((float) (DRAW_TIME - millisUntilFinished)) / (float) DRAW_TIME;
float length = measure.getLength() * percent;
measure.getSegment(start, length, segmentPath, true);
start = length;
missileDrawPath.addPath(segmentPath);
invalidate();
}
@Override
public void onFinish() {
measure.getSegment(start, measure.getLength(), segmentPath, true);
missileDrawPath.addPath(segmentPath);
invalidate();
}
};
timer.start();
}
@Override
public void onDraw(Canvas c) {
super.onDraw(c);
c.drawPath(missileDrawPath, mPaint);
}
基本上，计时器开始运行，并且取决于从missilePath检索段并将其添加到当前应绘制的路径所经过的时间。
答案 1 :(得分：0)
感谢SceLus工作得非常好，这里是人们最终遇到同样问题的完整代码。
类构造函数将Bezier曲线的起始和最终x和y作为输入，然后简单地计算中间控制点，然后根据SceLus代码绘制所有内容。
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.DashPathEffect;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.os.CountDownTimer;
import android.view.View;
public class DrawDottedCurve extends View {
Path path = new Path();
Path drawingPath = new Path();
Paint paint = new Paint();
float x1;
float y1;
float x3;
float y3;
public DrawDottedCurve(Context context, int a, int b, int c, int d) {
super(context);
x1 = a;
y1 = b;
x3 = c;
y3 = d;
paint.setAlpha(255);
paint.setStrokeWidth(2);
paint.setColor(Color.RED);
paint.setStyle(Style.STROKE);
paint.setPathEffect(new DashPathEffect(new float[] { 2, 4 }, 50));
path.moveTo(x1, y1); //
path.quadTo((x3 - x1) / 2, (y3 - y1) / 2, x3, y3); // Calculate Bezier Curve
final long DRAW_TIME = 10000;
CountDownTimer timer = new CountDownTimer(DRAW_TIME, 100) {
PathMeasure measure = new PathMeasure();
Path segmentPath = new Path();
float start = 0;
@Override
public void onTick(long millisUntilFinished) {
measure.setPath(path, false);
float percent = ((float) (DRAW_TIME - millisUntilFinished))
/ (float) DRAW_TIME;
float length = measure.getLength() * percent;
measure.getSegment(start, length, segmentPath, true);
start = length;
drawingPath.addPath(segmentPath);
invalidate();
}
@Override
public void onFinish() {
measure.getSegment(start, measure.getLength(), segmentPath,
true);
drawingPath.addPath(segmentPath);
invalidate();
}
};
timer.start();
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawPath(drawingPath, paint);
}
}