Null pointer exception when fade in animating in android studio

Question

I am making a fade-in animation to a textview in my project but the application crushes with a null pointer exception

the target is the last textview with id(long_click) and here is the xml file

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_more_options_passowrd_groups"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="arb.passwordmanager.more_options_passowrd_groups"
    android:background="@drawable/settings"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:orientation="vertical"
        android:background="#88FFFFFF"
        android:id="@+id/groups_layout">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20dp"
            android:text="@string/char_group"
            android:textColor="#222222"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/char_group_explain"
            android:textColor="#444444"/>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_marginTop="10dp"
            android:layout_height="wrap_content"
            android:id="@+id/checkboxes"
            android:orientation="vertical"
            ></LinearLayout>

        <View
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="#FF4444"></View>

            <CheckBox
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/check_uncheck_all"
                android:id="@+id/checkall"
                android:checked="true"
                android:textColor="#444444"
                />
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/long_click_item"
            android:textColor="#444444"
            android:id="@+id/long_click"/>


    </LinearLayout>

</RelativeLayout>

the animation xml is

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" android:duration="3000" >
<alpha android:fromAlpha="0" android:toAlpha="1" />

</set>

the function which calls the animation is

void text_fade_in()
    {
        TextView textView=(TextView) findViewById(R.id.long_click);
        Animation animation= AnimationUtils.loadAnimation(getBaseContext(),R.anim.fade_in);
        textView.startAnimation(animation);//the exception is here
    }

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
setContentView(R.layout.activity_more_options_passowrd_groups);
        text_fade_in();
    }

the animation file is located in R.anim.fade_in

the error is the following

E/AndroidRuntime: FATAL EXCEPTION: main
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{arb.passwordmanager/arb.passwordmanager.more_options_passowrd_groups}: java.lang.NullPointerException
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2255)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2309)
                      at android.app.ActivityThread.access$700(ActivityThread.java:157)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289)
                      at android.os.Handler.dispatchMessage(Handler.java:99)
                      at android.os.Looper.loop(Looper.java:176)
                      at android.app.ActivityThread.main(ActivityThread.java:5317)
                      at java.lang.reflect.Method.invokeNative(Native Method)
                      at java.lang.reflect.Method.invoke(Method.java:511)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
                      at dalvik.system.NativeStart.main(Native Method)
                   Caused by: java.lang.NullPointerException
                      at arb.passwordmanager.more_options_passowrd_groups.text_fade_in(more_options_passowrd_groups.java:170)
                      at arb.passwordmanager.more_options_passowrd_groups.onCreate(more_options_passowrd_groups.java:176)
                      at android.app.Activity.performCreate(Activity.java:5326)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2218)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2309) 
                      at android.app.ActivityThread.access$700(ActivityThread.java:157) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289) 
                      at android.os.Handler.dispatchMessage(Handler.java:99) 
                      at android.os.Looper.loop(Looper.java:176) 
                      at android.app.ActivityThread.main(ActivityThread.java:5317) 
                      at java.lang.reflect.Method.invokeNative(Native Method) 
                      at java.lang.reflect.Method.invoke(Method.java:511) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869) 
                      at dalvik.system.NativeStart.main(Native Method) 
I/Process: Sending signal. PID: 30468 SIG: 9
Disconnected from the target VM, address: 'localhost:8618', transport: 'socket'

I tried to change the target of the animation to another view in the same activity and yet getting the same result

after solving the problem the animation is not working as like there is no animation at all i updated the animation file to

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android"  android:fillBefore="true" android:interpolator="@android:anim/accelerate_interpolator" >
    <alpha android:fromAlpha="0" android:toAlpha="1" android:duration="3000" />

</set>

but still the animation is not working help me please

replace `yourXMLcontainsTextView` with your layout file name — Pavneet_Singh, Aug 18 '17 at 16:46

score 1 · Accepted Answer · answered Aug 18 '17 at 16:39

1

you forgot to call setContentView(R.layout.yourXMLcontainsTextView); before text_fade_in(); function call

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.yourXMLcontainsTextView); // add this , otherwise there is no design
    // linked with your activity and cannot be found using findViewById
    text_fade_in();
}

answered Aug 18 '17 at 16:39

Pavneet_Singh

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it partially works the application does not crush anymore but the animation is not running the target textview is remaining the same as if there is no animation – Ahmed Rajab Aug 18 '17 at 16:50
@AhmadRajab try adding the duration into `alpha` instead of `set` – Pavneet_Singh Aug 18 '17 at 16:58
still not working help please – Ahmed Rajab Aug 18 '17 at 17:03
@AhmadRajab if still doesn't work the add interpolator to define the appearance of your animation , https://stackoverflow.com/questions/8720626/android-fade-in-and-fade-out-with-imageview – Pavneet_Singh Aug 18 '17 at 17:04
is it related to fillbefore or fillafter properties of the animation xml i tried to make them true but still the same – Ahmed Rajab Aug 18 '17 at 17:04
still not working – Ahmed Rajab Aug 18 '17 at 17:33
post the updated code at the end of your question – Pavneet_Singh Aug 18 '17 at 17:46
you solved my main problem thank you very much I think the animation problem happens because the animation with onCreat I should make an independent thread for it – Ahmed Rajab Aug 19 '17 at 10:56
your activity and it's views are completely visible after on resume, so try overriding onresume and call `text_fade_in` from it otherwise last option is adding button and cllicklistener – Pavneet_Singh Aug 19 '17 at 12:01
1

I can not avoid onResume because it is essential for other features of the activity I solved the probele using onWindowFocusChange() listener and it works Thanks for your help – Ahmed Rajab Aug 19 '17 at 12:15

Null pointer exception when fade in animating in android studio

1 Answers1