Android动画无法点击

Question

My animation I'snt working on click, here is my code:

Edit: can now click the button, but nothing happens on click

animation: bottom_up.xml:

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
<translate android:fromYDelta="75%p" android:toYDelta="0%p"
    android:fillAfter="true"
    android:duration="500"/>

here is my java MusicPlayerActivity.java:

    btnPlayList.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Animation bottomUp = AnimationUtils.loadAnimation(MusicPlayerActivity.this, R.anim.bottom_up);
            ViewGroup hiddenPanel = (ViewGroup) v.findViewById(R.id.hidden_panel);
            hiddenPanel.startAnimation(bottomUp);
            hiddenPanel.setVisibility(View.VISIBLE);

        }
    });
} 

Thank you!

Answer 1

check if you initialed btnPlayList like this btnPlayList=(Button)findViewById(R.id.btnPlayList);

or hiddenPanel not exist in this view that you click on;

Answer 2

The error you are getting is a very common one. It's called NullPointerException because you try to call a method of an object whose reference is null, so the system can't resolve the method. You cand read more about this exception in this link .

The line that is probably causing this exception is:

ViewGroup hiddenPanel = (ViewGroup) v.findViewById(R.id.hidden_panel);

In order to fix it, I would suggest two things:

• Check that the id R.id.hidden_panel is correct.

• If you are contemplating that R.id.hidden_panel might not be in your layout, wrap its usage with a null check:

   if (hiddenPanel != null) { hiddenPanel.startAnimation(bottomUp); hiddenPanel.setVisibility(View.VISIBLE); } 

EDIT:

To fix the animation not showing, try calling startAnimation after you set the hiddenPanel to Visible, and not before.

Answer 3

java.lang.NullPointerException -> some variables not initialized. check all variables