今天看到一个银行的APP上面的loadingview 挺好的，就尝试着自己实现，觉得很简单，但自己实现起来还是发现了一些问题。

LoadingView和下图类似：

实现的代码也不是很复杂，就是小球的运动轨迹需要计算，我自己手画了个计算的图，很简单的就是三角函数的使用。

然后代码就是代码实现了，主要的内容都有注释，代码如下：

public class LoadingView extends View { private final static String TAG = "LoadingView"; private final static int LEFT_BALL_DOWN = 1; private final static int LEFT_BALL_UP = 2; private final static int RIGHT_BALL_DOWN = 3; private final static int RIGHT_BALL_UP = 4; private Paint paint1, paint2, paint3, paint4, paint5; private int mCurrentAnimatorValue; private int circleRadius = 10; //小球的半径 private int distance = 60; //小球开始下落到最低点的距离 private int mCurrentState = LEFT_BALL_DOWN; public LoadingView(Context context) { super(context); init(context); } public LoadingView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); init(context); } public LoadingView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(context); } private void init(Context context) { paint1 = getPaint(Color.RED); paint2 = getPaint(Color.YELLOW); paint3 = getPaint(Color.GREEN); paint4 = getPaint(Color.BLUE); paint5 = getPaint(Color.CYAN); ValueAnimator animator = ValueAnimator.ofInt(0, 90); animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { mCurrentAnimatorValue = (int) animation.getAnimatedValue(); Log.e(TAG, "onAnimationUpdate : mCurrentAnimatorValue = " + mCurrentAnimatorValue); invalidate(); } }); animator.addListener(new Animator.AnimatorListener() { @Override public void onAnimationStart(Animator animation) { } @Override public void onAnimationEnd(Animator animation) { } @Override public void onAnimationCancel(Animator animation) { } @Override public void onAnimationRepeat(Animator animation) { Log.e(TAG, "onAnimationRepeat : mCurrentAnimatorValue = " + mCurrentAnimatorValue); switch (mCurrentState) { case LEFT_BALL_DOWN: mCurrentState = RIGHT_BALL_UP; break; case RIGHT_BALL_UP: mCurrentState = RIGHT_BALL_DOWN; break; case RIGHT_BALL_DOWN: mCurrentState = LEFT_BALL_UP; break; case LEFT_BALL_UP: mCurrentState = LEFT_BALL_DOWN; break; } } }); animator.setStartDelay(500); animator.setDuration(600); animator.setRepeatCount(ValueAnimator.INFINITE); animator.setInterpolator(new DecelerateInterpolator()); animator.start(); } private Paint getPaint(int color) { Paint paint = new Paint(); paint.setColor(color); paint.setAntiAlias(true); paint.setStyle(Paint.Style.FILL); return paint; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); int x, y; double cosValue = Math.cos(PI * mCurrentAnimatorValue / 180); double sinValue = Math.sin(PI * mCurrentAnimatorValue / 180); drawFourBall(canvas); switch (mCurrentState) { case LEFT_BALL_DOWN://最左边小球往下撞击 x = circleRadius + (int) ((distance - circleRadius) * (1 - cosValue)); y = getHeight() - distance + (int) ((distance - circleRadius) * sinValue); canvas.drawCircle(x, y, circleRadius, paint1); break; case RIGHT_BALL_UP://最右边小球往上撞击 x = distance + 8 * circleRadius + (int) ((distance - circleRadius) * sinValue); y = getHeight() - distance + (int) (cosValue * (distance - circleRadius)); canvas.drawCircle(x, y, circleRadius, paint5); break; case RIGHT_BALL_DOWN://最右边小球往下撞击 x = distance + 8 * circleRadius + (int) ((distance - circleRadius) * (cosValue)); y = (getHeight() - distance) + (int) ((distance - circleRadius) * (sinValue)); canvas.drawCircle(x, y, circleRadius, paint5); break; case LEFT_BALL_UP://最左边小球往上撞击 x = distance - (int) ((distance - circleRadius) * sinValue); y = getHeight() - distance + (int) ((distance - circleRadius) * cosValue); canvas.drawCircle(x, y, circleRadius, paint1); break; } } private void drawFourBall(Canvas canvas) { int y = getHeight() - circleRadius; canvas.drawCircle(distance + 2 * circleRadius, y, circleRadius, paint2); canvas.drawCircle(distance + 4 * circleRadius, y, circleRadius, paint3); canvas.drawCircle(distance + 6 * circleRadius, y, circleRadius, paint4); if (mCurrentState == LEFT_BALL_DOWN || mCurrentState == LEFT_BALL_UP) {//最左边球运动的时候，要绘制最右边的球 canvas.drawCircle(distance + 8 * circleRadius, y, circleRadius, paint5); } else if (mCurrentState == RIGHT_BALL_UP || mCurrentState == RIGHT_BALL_DOWN) {//最右边球运动的时候，要绘制最左边的球 canvas.drawCircle(distance, y, circleRadius, paint1); } }}

实现的效果如图一，有问题的话互相讨论。最后贴上想xml文件，后续会完善设置loadingview的大小和颜色之类的参数。
xml如下：

<com.define_view.LoadingView android:layout_marginTop="20px" android:background="#999999" android:layout_width="200px" android:layout_height="200px" />

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。