今天学习了Evaluator自定义。
定义一个对象Point.java,对象中只有x,y两个属性以及get,set方法~
public class Point { private float x; private float y; public Point() { } public Point(float x, float y) { this.x = x; this.y = y; } public float getX() { return x; } public float getY() { return y; } public void setX(float x) { this.x = x; } public void setY(float y) { this.y = y; } }
接着自定义Evaluator类:PointEvaluator.java,实现接口重写evaluate方法~
public class PointEvaluator implements TypeEvaluator<Point>{ @Override public Point evaluate(float fraction, Point startValue, Point endValue) { float x = startValue.getX() + fraction * (endValue.getX() - startValue.getX()); float y = startValue.getY() + fraction * (endValue.getY() - startValue.getY()); Point point = new Point(x, y); return point; } }
然后自定义一个View类:AnimView.java,很简单~
public class AnimView extends View { public static final float RADIUS = 80.0f; private Point currentPoint; private Paint mPaint; public AnimView(Context context) { this(context, null); } public AnimView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public AnimView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } private void init() { mPaint = new Paint(Paint.ANTI_ALIAS_FLAG); mPaint.setColor(Color.BLUE); } private void drawCircle(Canvas canvas){ float x = currentPoint.getX(); float y = currentPoint.getY(); canvas.drawCircle(x, y, RADIUS, mPaint); } private void startAnimation() { Point startPoint = new Point(RADIUS, RADIUS); Point endPoint = new Point(getWidth() - RADIUS, getHeight() - RADIUS); ValueAnimator anim = ValueAnimator.ofObject(new PointEvaluator(), startPoint, endPoint); anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { currentPoint = (Point) animation.getAnimatedValue(); invalidate(); } }); anim.setDuration(3000l); anim.start(); } @Override protected void onDraw(Canvas canvas) { if (currentPoint == null) { currentPoint = new Point(RADIUS, RADIUS); drawCircle(canvas); startAnimation(); } else { drawCircle(canvas); } } }
最后MainActivity.java处实例化这个View即可~
public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new AnimView(this)); } }