Android利用动画实现背景逐渐变暗
前言
之前写了一篇Android-实现底部弹出PopupWindow并让背景逐渐变暗,介绍利用Handler动态改变背景透明度从而达到变暗的效果。现在补充一种方法,使用动画来实现相同的效果。
ValueAnimator 和 Interpolator
今天的主角就是这俩,关于ValueAnimator和Interpolator(插值器)的概念请各位自行补充,这里主要讲述怎么用到我们这里来(因为我也不很懂(捂脸))。
效果
跟之前没有太大区别,只是为了演示变暗、变亮的过程 ↓
代码
AnimUtil.java
/** * 动画工具类 * UpdateListener: 动画过程中通过添加此监听来回调数据 * EndListener: 动画结束的时候通过此监听器来做一些处理 */ public class AnimUtil { private ValueAnimator valueAnimator; private UpdateListener updateListener; private EndListener endListener; private long duration; private float start; private float end; private Interpolator interpolator = new LinearInterpolator(); public AnimUtil() { duration = 1000; //默认动画时常1s start = 0.0f; end = 1.0f; interpolator = new LinearInterpolator();// 匀速的插值器 } public void setDuration(int timeLength) { duration = timeLength; } public void setValueAnimator(float start, float end, long duration) { this.start = start; this.end = end; this.duration = duration; } public void setInterpolator(Interpolator interpolator) { this.interpolator = interpolator; } public void startAnimator() { if (valueAnimator != null){ valueAnimator = null; } valueAnimator = ValueAnimator.ofFloat(start, end); valueAnimator.setDuration(duration); valueAnimator.setInterpolator(interpolator); valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator valueAnimator) { if (updateListener == null) { return; } float cur = (float) valueAnimator.getAnimatedValue(); updateListener.progress(cur); } }); valueAnimator.addListener(new Animator.AnimatorListener() { @Override public void onAnimationStart(Animator animator) {} @Override public void onAnimationEnd(Animator animator) { if(endListener == null){ return; } endListener.endUpdate(animator); } @Override public void onAnimationCancel(Animator animator) {} @Override public void onAnimationRepeat(Animator animator) {} }); valueAnimator.start(); } public void addUpdateListener(UpdateListener updateListener) { this.updateListener = updateListener; } public void addEndListner(EndListener endListener){ this.endListener = endListener; } public interface EndListener { void endUpdate(Animator animator); } public interface UpdateListener { void progress(float progress); } }
MainActivity.java
public class MainActivity extends AppCompatActivity { private AnimUtil animUtil; private float bgAlpha = 1f; private boolean bright = false; PopupWindow popupWindow; Button button; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); animUtil = new AnimUtil(); button = (Button) findViewById(R.id.btn); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { bottomwindow(button); toggleBright(); } }); } private void toggleBright() { //三个参数分别为: 起始值 结束值 时长 那么整个动画回调过来的值就是从0.5f--1f的 animUtil.setValueAnimator(0.5f, 1f, 350); animUtil.addUpdateListener(new AnimUtil.UpdateListener() { @Override public void progress(float progress) { //此处系统会根据上述三个值,计算每次回调的值是多少,我们根据这个值来改变透明度 bgAlpha = bright ? progress : (1.5f - progress);//三目运算,应该挺好懂的。 backgroundAlpha(bgAlpha);//在此处改变背景,这样就不用通过Handler去刷新了。 } }); animUtil.addEndListner(new AnimUtil.EndListener() { @Override public void endUpdate(Animator animator) { //在一次动画结束的时候,翻转状态 bright = !bright; } }); animUtil.startAnimator(); } /*** * 此方法用于改变背景的透明度,从而达到“变暗”的效果 */ private void backgroundAlpha(float bgAlpha) { WindowManager.LayoutParams lp = getWindow().getAttributes(); lp.alpha = bgAlpha; //0.0-1.0 getWindow().setAttributes(lp); getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND); } void bottomwindow(View view) { if (popupWindow != null && popupWindow.isShowing()) { return; } LinearLayout layout = (LinearLayout) getLayoutInflater().inflate(R.layout.window_popup, null); popupWindow = new PopupWindow(layout, ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT); //点击空白处时,隐藏掉pop窗口 popupWindow.setFocusable(true); popupWindow.setBackgroundDrawable(new BitmapDrawable()); popupWindow.setAnimationStyle(R.style.Popupwindow); int[] location = new int[2]; view.getLocationOnScreen(location); popupWindow.showAtLocation(view, Gravity.LEFT | Gravity.BOTTOM, 0, -location[1]); popupWindow.setOnDismissListener(new PopupWindow.OnDismissListener() { @Override public void onDismiss() { toggleBright(); } }); } }
代码很简单,注释都写了。
小结:
对比之前的那种用Handler的方法写的,这种感觉代码更简洁,更容易在多处使用,也算是填坑吧,哈哈。 如果本文埋下了另一个坑,请大家指正,谢谢!
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