这是一个很简单的动画效果,使用属性动画便可实现,但愿对读者学习动画能达到抛砖引玉的效果java
如上是咱们须要作的一个Loading动画。Loading效果是很常见的一种动画,最简单的实现让设计画个动态图便可,或者画个静态图而后使用帧动画也能够实现。可是今天咱们用纯代码实现,不用任何图片资源。
canvas
绘制两个不一样半径的弧形
首先初始化外圆和内园的Recf();性能优化
private RectF mOuterCircleRectF = new RectF();
private RectF mInnerCircleRectF = new RectF();
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而后在onDraw方法绘制圆弧:架构
//获取View的中心
float centerX = getWidth() / 2;
float centerY = getHeight() / 2;
if (lineWidth > centerX) {
throw new IllegalArgumentException("lineWidth值太大了");
}
//外圆半径,由于咱们的弧形是有宽度的,因此计算半径的时候应该把这部分减去,否则会有切割的效果
float outR = centerX - lineWidth;
//小圆半径
float inR = outR * 0.6f - lineWidth;
//设置弧形的距离上下左右的距离,也就是包围园的矩形。
mOuterCircleRectF.set(centerX - outR, centerY - outR, centerX + outR, centerY + outR);
mInnerCircleRectF.set(centerX - inR, centerY - inR, centerX + inR, centerY + inR);
//绘制外圆
canvas.drawArc(mOuterCircleRectF, mRotateAngle % 360, OUTER_CIRCLE_ANGLE, false, mStrokePaint);
//绘制内圆
canvas.drawArc(mInnerCircleRectF, 270 - mRotateAngle % 360, INTER_CIRCLE_ANGLE, false, mStrokePaint);
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代码很简单,就像注释同样:ide
绘制圆的过程应该放在onDraw方法中,这样咱们能够不断的重绘,也能够获取view的真实的宽高性能
固然,咱们还需设置一个画笔来画咱们的圆学习
mStrokePaint = new Paint();
mStrokePaint.setStyle(Paint.Style.STROKE);
mStrokePaint.setStrokeWidth(lineWidth);
mStrokePaint.setColor(color);
mStrokePaint.setAntiAlias(true);
mStrokePaint.setStrokeCap(Paint.Cap.ROUND);
mStrokePaint.setStrokeJoin(Paint.Join.ROUND);
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圆弧画好了,而后利用属性动画便可实现动画效果。这里采用的是ValueAnimator,值属性动画,咱们能够设置一个值范围,而后让他在这个范围内变化。优化
mFloatValueAnimator = ValueAnimator.ofFloat(0.0f, 1.0f);
mFloatValueAnimator.setRepeatCount(Animation.INFINITE);
mFloatValueAnimator.setDuration(ANIMATION_DURATION);
mFloatValueAnimator.setStartDelay(ANIMATION_START_DELAY);
mFloatValueAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
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这个设置很简单,设置值得范围,这是无线循环,设置动画执行的时间,这只动画循环时延迟的时间,设置插值器。动画
让弧形动起来的原理,就是监听值属性动画的值变化,而后在这个变化的过程当中不断的改变弧形的角度,而后让它重绘便可。ui
咱们让咱们的loadview实现ValueAnimator.AnimatorUpdateListener接口,而后在onAnimationUpdate监听动画的变化。咱们初始化值属性动画的时候设置了值得范围为float型,因此这里能够获取这个变化的值。而后利用这个值能够改变绘制圆的角度大小,再调用重绘方法,便可实现:
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mRotateAngle = 360 * (float)animation.getAnimatedValue();
invalidate();
}
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整个思路大体就是这样。完整代码以下:
public class LoadingView extends View implements Animatable, ValueAnimator.AnimatorUpdateListener {
private static final long ANIMATION_START_DELAY = 200;
private static final long ANIMATION_DURATION = 1000;
private static final int OUTER_CIRCLE_ANGLE = 270;
private static final int INTER_CIRCLE_ANGLE = 90;
private ValueAnimator mFloatValueAnimator;
private Paint mStrokePaint;
private RectF mOuterCircleRectF;
private RectF mInnerCircleRectF;
private float mRotateAngle;
public LoadingView (Context context) {
this(context, null);
}
public LoadingView (Context context, @Nullable AttributeSet attrs) {
this(context, attrs, -1);
}
public LoadingView (Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, -1);
}
public LoadingView (Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
initView(context, attrs);
}
float lineWidth;
private void initView(Context context, AttributeSet attrs) {
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.MyCustomLoadingView);
lineWidth = typedArray.getFloat(R.styleable.MyCustomLoadingView_lineWidth, 10.0f);
int color = typedArray.getColor(R.styleable.MyCustomLoadingView_viewColor, context.getColor(R.color.colorAccent));
typedArray.recycle();
initAnimators();
mOuterCircleRectF = new RectF();
mInnerCircleRectF = new RectF();
//初始化画笔
initPaint(lineWidth, color);
//旋转角度
mRotateAngle = 0;
}
private void initAnimators() {
mFloatValueAnimator = ValueAnimator.ofFloat(0.0f, 1.0f);
mFloatValueAnimator.setRepeatCount(Animation.INFINITE);
mFloatValueAnimator.setDuration(ANIMATION_DURATION);
mFloatValueAnimator.setStartDelay(ANIMATION_START_DELAY);
mFloatValueAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
}
/** * 初始化画笔 */
private void initPaint(float lineWidth, int color) {
mStrokePaint = new Paint();
mStrokePaint.setStyle(Paint.Style.STROKE);
mStrokePaint.setStrokeWidth(lineWidth);
mStrokePaint.setColor(color);
mStrokePaint.setAntiAlias(true);
mStrokePaint.setStrokeCap(Paint.Cap.ROUND);
mStrokePaint.setStrokeJoin(Paint.Join.ROUND);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
float centerX = getWidth() / 2;
float centerY = getHeight() / 2;
//最大尺寸
if (lineWidth > centerX) {
throw new IllegalArgumentException("lineWidth值太大了");
}
float outR = centerX - lineWidth;
//小圆尺寸
float inR = outR * 0.6f;
mOuterCircleRectF.set(centerX - outR, centerY - outR, centerX + outR, centerY + outR);
mInnerCircleRectF.set(centerX - inR, centerY - inR, centerX + inR, centerY + inR);
//先保存画板的状态
canvas.save();
//外圆
canvas.drawArc(mOuterCircleRectF, mRotateAngle % 360, OUTER_CIRCLE_ANGLE, false, mStrokePaint);
//内圆
canvas.drawArc(mInnerCircleRectF, 270 - mRotateAngle % 360, INTER_CIRCLE_ANGLE, false, mStrokePaint);
//恢复画板的状态
canvas.restore();
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
startLoading();
}
public void startLoading() {
start();
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
stopLoading();
}
public void stopLoading() {
stop();
}
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mRotateAngle = 360 * (float)animation.getAnimatedValue();
invalidate();
}
protected void computeUpdateValue(float animatedValue) {
mRotateAngle = (int) (360 * animatedValue);
}
@Override
public void start() {
if (mFloatValueAnimator.isStarted()) {
return;
}
mFloatValueAnimator.addUpdateListener(this);
mFloatValueAnimator.setRepeatCount(Animation.INFINITE);
mFloatValueAnimator.setDuration(ANIMATION_DURATION);
mFloatValueAnimator.start();
}
@Override
public void stop() {
mFloatValueAnimator.removeAllUpdateListeners();
mFloatValueAnimator.removeAllListeners();
mFloatValueAnimator.setRepeatCount(0);
mFloatValueAnimator.setDuration(0);
mFloatValueAnimator.end();
}
@Override
public boolean isRunning() {
return mFloatValueAnimator.isRunning();
}
}
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attr文件代码以下:
<declare-styleable name="LoadingView">
<attr name="lineWidth" format="float" />
<attr name="viewColor" format="color" />
</declare-styleable>复制代码
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