setColorFilter shows a null object reference

Issue

I create a layout resource file named btn.xml, it contains ImageView. in main activity i inflate btn.xml in content_main.xml and i try to set background of inflated View. but it shows me : Drawable.setColorFilter(int, android.graphics.PorterDuff$Mode)' on a null object reference

code java in mainActivity :

View v;
RelativeLayout rlt;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    LayoutInflater myInflater = (LayoutInflater) getApplicationContext().getSystemService(getApplicationContext().LAYOUT_INFLATER_SERVICE);
    v = myInflater.inflate(R.layout.btn,null,false);
    // Here is the probelm :
    v.getBackground().setColorFilter(Color.parseColor("#00ff00"), PorterDuff.Mode.DARKEN);
    rlt = (RelativeLayout) findViewById(R.id.rlt);
    rlt.addView(v);
}

content_main.xml Layout :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    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"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.othma.tjkljklj.MainActivity"
    tools:showIn="@layout/activity_main"
    android:id="@+id/rlt">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/textView" />

</RelativeLayout>

btn.xml layout Resource file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:weightSum="1">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imgv1"
        android:src="@drawable/continu" />
</LinearLayout>

Solution

in your btn.xml file as you see you did not set any drawable to your view(linearlayout), so you got a null object reference error.

setColorFilter() method specify a color and Porter-Duff mode to be the color filter for drawable.

For example; if you want to change imageview drawable(or any view drawable) color, you should use setColorFilter() method.

imageview.getDrawable().setColorFilter(color, mode);

if you want to change background color of your view, then you should use setBackgroundColor() method.

view.setBackgroundColor(getResources().getColor(R.color.anycolor)); 

Answered By - settaratici