前言
之前寫了一篇Android-實作底部彈出PopupWindow并讓背景逐漸變暗，介紹利用Handler動态改變背景透明度進而達到變暗的效果。現在補充一種方法，使用動畫來實作相同的效果。
ValueAnimator和 Interpolator
今天的主角就是這倆，關于ValueAnimator和Interpolator(插值器)的概念請各位自行補充，這裡主要講述怎麼用到我們這裡來(因為我也不很懂(捂臉))。
效果
跟之前沒有太大差別，隻是為了示範變暗、變亮的過程 ↓
代碼
AnimUtil.java
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; //預設動畫時常1s
start = 0.0f;
end = 1.0f;
interpolator = new LinearInterpolator();// 勻速的插值器
}
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() {
//三個參數分别為： 起始值 結束值 時長 那麼整個動畫回調過來的值就是從0.5f--1f的
animUtil.setValueAnimator(0.5f, 1f, 350);
animUtil.addUpdateListener(new AnimUtil.UpdateListener() {
@Override
public void progress(float progress) {
//此處系統會根據上述三個值，計算每次回調的值是多少，我們根據這個值來改變透明度
bgAlpha = bright ? progress : (1.5f - progress);//三目運算，應該挺好懂的。
backgroundAlpha(bgAlpha);//在此處改變背景，這樣就不用通過Handler去重新整理了。
}
});
animUtil.addEndListner(new AnimUtil.EndListener() {
@Override
public void endUpdate(Animator animator) {
//在一次動畫結束的時候，翻轉狀态
bright = !bright;
}
});
animUtil.startAnimator();
}
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);
//點選空白處時，隐藏掉pop視窗
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();
}
});
}
}
代碼很簡單，注釋都寫了。
小結：
對比之前的那種用Handler的方法寫的，這種感覺代碼更簡潔，更容易在多處使用，也算是填坑吧，哈哈。 如果本文埋下了另一個坑，請大家指正，謝謝！
以上就是本文的全部内容，希望對大家的學習有所幫助，也希望大家多多支援腳本之家。