What is ButterKnife?

Its a kind of view injection in Activities or Fragments using Annotations.

Butterknife can be used to

1. Bind Views
2. Bind Clicks
3. Can be used with resources like strings, colors, Dimens, Drawables etc.

Below are the annotations available

AnnotationDescription

@BindView	Binds view object. TextView, Button, Spinner or any view object @BindView(R.id.logo) ImageView imgLogo;
@BindViews	Binds array of views into List @BindViews({R.id.lbl_name, R.id.lbl_email, R.id.lbl_address}) List lblArray;
@BindDrawable	Binds drawable element. Loads the drawable image from res folder @BindDrawable(R.mipmap.ic_launcher) Drawable drawableLogo;
@BindString	Binds string resource @BindString(R.string.app_name) String appName;
@BindColor	Binds color resource @BindColor(R.color.colorPrimaryDark) int colorTitle;
@BindDimen	Binds dimen resource @BindDimen(R.id.padding_hori) float paddingHorizontal;
@BindAnim	Binds animation from anim resource @BindAnim(R.anim.move_up) Animation animMoveUp;
@BindBitmap	Binds bitmap object. @BindBitmap(R.mipmap.ic_launcher) Bitmap logo;
@BindFont	Binds font resource @BindViews({R.id.lbl_name, R.id.lbl_email, R.id.lbl_address}) List lblArray;
@BindFloat	Binds float value @BindFloat(R.dimen.radius) float radius;
@BindInt Binds	int resource @BindInt(R.integer.distance) int distance;

Code

Let’s start with the build.gradle
Add below code in the dependencies.

compile 'com.jakewharton:butterknife:8.8.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

Example

Lets take an example of Activity

Layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="20dp">

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

    <EditText
        android:id="@+id/edName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btnClick"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Click Me" />

    <ImageView
        android:id="@+id/imgView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />


    <TextView
        android:id="@+id/tvTitle1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello" />


    <TextView
        android:id="@+id/tvTitle2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello" />


    <TextView
        android:id="@+id/tvTitle3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello" />
</LinearLayout>

MainActivity

package butterknife_demo.coderzheaven.com.butterknifedemo;

import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

import butterknife.BindColor;
import butterknife.BindDrawable;
import butterknife.BindView;
import butterknife.BindViews;
import butterknife.ButterKnife;
import butterknife.OnClick;

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.tvTitle)
    TextView tvTitle;

    @BindView(R.id.edName)
    EditText edName;

    @BindView(R.id.imgView)
    ImageView imgView;

    @BindDrawable(R.mipmap.ic_launcher)
    Drawable drawableLogo;

    @BindColor(R.color.colorPrimaryDark)
    int colorTitle;

    @BindViews({R.id.tvTitle1, R.id.tvTitle2, R.id.tvTitle3})
    List<TextView> tvTitleArray;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);

        tvTitle.setTextColor(colorTitle);

        imgView.setImageDrawable(drawableLogo);

        final String[] tvText = new String[]{"Hello", "Coderz", "Heaven"};

        ButterKnife.Action<TextView> texts = new ButterKnife.Action<TextView>() {
            @Override
            public void apply(TextView view, int index) {
                view.setText(tvText[index]);
            }
        };

        // setting text to array of textviews
        ButterKnife.apply(tvTitleArray, texts);
    }

    @OnClick(R.id.btnClick)
    public void onButtonClick(View view) {
        Toast.makeText(getApplicationContext(), "Name : " + edName.getText().toString(),
                Toast.LENGTH_SHORT).show();
    }
}

Fragment

If this is a fragment, then the code will change like this

public class MyFragment extends Fragment {
 
    Unbinder unbinder;
 
    @BindView(R.id.txtName)
    TextView txtName;
 
    @BindView(R.id.btnEnter)
    Button btnEnter;
 
    @BindView(R.id.edName)
    EditText edName;
 
    public MyFragment() {
    }
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
    }
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.my_frag_layout, container, false);
 
        // bind view using butter knife
        unbinder = ButterKnife.bind(this, view);
 
        return view;
    }
 
    @Override
    public void onDestroyView() {
        super.onDestroyView();
        unbinder.unbind();
    }
}

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