無法使用ObjectAnimator沿着Android中的路徑移動和設置ImageView的動畫效果

Question

我試圖使用ObjectAnimator沿着path移動ImageView。我正面臨着NPE。這是我正在嘗試的代碼。

path = new Path(); 
path.moveTo((float)(maxX/2)+(maxX/4),maxY/4); 
path.quadTo((float)(maxX/2)+(maxX/4),maxY/4, (float)(maxX/2)+(maxX/4)+30,maxY/2); 

ObjectAnimator animator = new ObjectAnimator(); 
     animator.ofFloat(img,View.X,View.Y,path); 
     animator.setDuration(1000); 
     animator.setStartDelay(600); 
     animator.start(); 

的exception是：

Caused by: java.lang.NullPointerException: Attempt to get length of null array 
at android.animation.ValueAnimator.initAnimation(ValueAnimator.java:534) 
at android.animation.ObjectAnimator.initAnimation(ObjectAnimator.java:880) 
at android.animation.ValueAnimator.setCurrentFraction(ValueAnimator.java:610) 
at android.animation.ValueAnimator.setCurrentPlayTime(ValueAnimator.java:589) 
at android.animation.ValueAnimator.start(ValueAnimator.java:1106) 
at android.animation.ValueAnimator.start(ValueAnimator.java:1117) 
at android.animation.ObjectAnimator.start(ObjectAnimator.java:852) 
at com.example.user.curveanimation.MainActivity.onCreate(MainActivity.java:48) 
at android.app.Activity.performCreate(Activity.java:6251) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2403) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)  
at android.app.ActivityThread.-wrap11(ActivityThread.java)  
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)  
at android.os.Handler.dispatchMessage(Handler.java:102)  
at android.os.Looper.loop(Looper.java:148)  
at android.app.ActivityThread.main(ActivityThread.java:5461)  
at java.lang.reflect.Method.invoke(Native Method)  

如果有什麼事我做錯了，有人可以幫我通過路徑動畫。 SOmebody，請幫助！謝謝。

Answer 1

我有動畫ImageButton1

TranslateAnimation a = new TranslateAnimation(0, amountToMove, 0, 0); 
          a.setDuration(1000); 

          // Finalize movement when animation ends 
          a.setAnimationListener(new Animation.AnimationListener() { 
           @Override 
           public void onAnimationEnd(Animation animation) { 
            RelativeLayout.LayoutParams rp = (RelativeLayout.LayoutParams) imageButton1.getLayoutParams(); 
            // Restore measured width and change left margin 
            //rp.width = mButtonWidth; 
            try { 
             rp.leftMargin = rp.leftMargin + amountToMove; 
             imageButton1.setLayoutParams(rp); 
             // amountToMove = -amountToMove; 
            } finally{ 
             Context context = getApplicationContext(); 



            } 

           } 

           @Override 
           public void onAnimationStart(Animation animation) { /* Do nothing */ 
           RelativeLayout.LayoutParams rp=(RelativeLayout.LayoutParams)imageButton1.getLayoutParams(); 
           imageButton1.setLayoutParams(rp); 
           } 

           @Override 
           public void onAnimationRepeat(Animation animation) { /* Do nothing */ } 
          }); 
          imageButton1.startAnimation(a);