butter knife tutorial android

What is Butter knife : 

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•   Butter-knife is a library it was developed by  Jake Wharton at Square. 
•   Butter-knife is used for remove repetitive lines of code for Binding views (like : TextView txtView = findViewById(R.id.txtView);
• 
  

How To Import Butter-knife in Android Project :

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implementation 'com.jakewharton:butterknife:(insert latest version)'

annotationProcessor 'com.jakewharton:butterknife-compiler:(insert latest version)'

Link :https://jakewharton.github.io/butterknife/

Where We use :

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• View Binding 
• Event binding 
• Resource Binding 

View Binding:

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• @Bindview is butter-knife annotation it used for bind-views like text-view,button-view,edit-text .
• Butter knife automatically finds view and it convert into specified view. 

 example : 

activit_main.xml

<?xml version="1.0" encoding="utf-8"?>

<android.support.constraint.ConstraintLayout 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"

    tools:context=".MainActivity">

    <TextView

        android:id="@+id/txtView"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Hello World!"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.txtView)

    TextView txtView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        ButterKnife.bind(this);

        txtView.setText(" Hello From Butter Knife ");

    }

}

Resource Binding :

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• @BindBool, @BindColor, @BindDimen, @BindDrawable, @BindInt, @BindString are annotations from butter-knife used for bind resources.

Sample 

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.txtView)

    TextView txtView;

    @BindDrawable(R.mipmap.ic_launcher)

    Drawable img;

    @BindString(R.string.str_butterknife)

    String str_intro;

    @BindColor(R.color.colorAccent)

    int color;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        ButterKnife.bind(this);

        txtView.setText(str_intro);

    }

}

 

How to Bind butter-knife in activity and Fragment :

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In Activity : 

@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    ButterKnife.bind(this);

}

in fragment : 

@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.fancy_fragment, container, false);

    ButterKnife.bind(this, view);

    return view;

  }

In Adapter 

static class ViewHolder {

    @BindView(R.id.title) TextView name;

    @BindView(R.id.job_title) TextView jobTitle;

    public ViewHolder(View view) {

      ButterKnife.bind(this, view);

    }

  }

how to perform click events using Butter-knife :

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public class MainActivity extends AppCompatActivity {

    @BindView(R.id.txtView)

    TextView txtView;

    @BindView(R.id.btn_button)

    Button btn_button;

    @BindDrawable(R.mipmap.ic_launcher)

    Drawable img;

    @BindString(R.string.str_butterknife)

    String str_intro;

    @BindString(R.string.str_hai)

    String str_hai;

    @BindColor(R.color.colorAccent)

    int color;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        ButterKnife.bind(this);

        txtView.setText(str_intro);

    }

    @OnClick(R.id.btn_button)

    public void sayHello() {

        txtView.setText(str_hai);

    }

}

What is Optional Binding in Butter-Knife :

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When we using Bind-view exception throws if target was not found , to overcome we have@Nullable and @Optional annotations in butter knife 

• @Nullable used for  fields

@Nullable @BindView(R.id.might_not_be_there) TextView mightNotBeThere;

@Optional @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {

  // TODO ...

}