• Monday, March 20, 2017

    Android - New and easy way to handle findViewById.

    Field and Method binding method for android.

    A very easy method to bind your views to class.  It uses annotate fields @BindView and a view ID that automatically cast your view to field. 


    Old codes:

    class MyActivity extends Activity{
        Textview m1, m2;

        @Override
        protected void onCreate(.......){
          ..........
          ..........
          m1 =(TextView) findViewById(R.id.tv_m1);
          m2 =(TextView) findViewById(R.id.tv_m2);
       }
    }

    New way to write this code:

    class MyActivity extends Activity{
        @BindView(R.id.tv_m1) TextView m1;
        @BindView(R.id.tv_m2) TextView m2;
        
        @Override
        protected void onCreate(.....){
            .........
            .........
            ButterKnife.bind(this);
        }

    }




    Introduction

    Annotate fields with @BindView and a view ID for Butter Knife to find and automatically cast the corresponding view in your layout.
    class ExampleActivity extends Activity {
      @BindView(R.id.title) TextView title;
      @BindView(R.id.subtitle) TextView subtitle;
      @BindView(R.id.footer) TextView footer;
    
      @Override public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.simple_activity);
        ButterKnife.bind(this);
        // TODO Use fields...
      }
    }
    Instead of slow reflection, code is generated to perform the view look-ups. Calling bind delegates to this generated code that you can see and debug.
    The generated code for the above example is roughly equivalent to the following:
    public void bind(ExampleActivity activity) {
      activity.subtitle = (android.widget.TextView) activity.findViewById(2130968578);
      activity.footer = (android.widget.TextView) activity.findViewById(2130968579);
      activity.title = (android.widget.TextView) activity.findViewById(2130968577);
    }

    RESOURCE BINDING

    Bind pre-defined resources with @BindBool@BindColor@BindDimen@BindDrawable@BindInt@BindString, which binds an R.bool ID (or your specified type) to its corresponding field.
    class ExampleActivity extends Activity {
      @BindString(R.string.title) String title;
      @BindDrawable(R.drawable.graphic) Drawable graphic;
      @BindColor(R.color.red) int red; // int or ColorStateList field
      @BindDimen(R.dimen.spacer) Float spacer; // int (for pixel size) or float (for exact value) field
      // ...
    }

    NON-ACTIVITY BINDING

    You can also perform binding on arbitrary objects by supplying your own view root.
    public class FancyFragment extends Fragment {
      @BindView(R.id.button1) Button button1;
      @BindView(R.id.button2) Button button2;
    
      @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fancy_fragment, container, false);
        ButterKnife.bind(this, view);
        // TODO Use fields...
        return view;
      }
    }
    Another use is simplifying the view holder pattern inside of a list adapter.
    public class MyAdapter extends BaseAdapter {
      @Override public View getView(int position, View view, ViewGroup parent) {
        ViewHolder holder;
        if (view != null) {
          holder = (ViewHolder) view.getTag();
        } else {
          view = inflater.inflate(R.layout.whatever, parent, false);
          holder = new ViewHolder(view);
          view.setTag(holder);
        }
    
        holder.name.setText("John Doe");
        // etc...
    
        return view;
      }
    
      static class ViewHolder {
        @BindView(R.id.title) TextView name;
        @BindView(R.id.job_title) TextView jobTitle;
    
        public ViewHolder(View view) {
          ButterKnife.bind(this, view);
        }
      }
    }
    You can see this implementation in action in the provided sample.
    Calls to ButterKnife.bind can be made anywhere you would otherwise put findViewById calls.
    Other provided binding APIs:
    • Bind arbitrary objects using an activity as the view root. If you use a pattern like MVC you can bind the controller using its activity with ButterKnife.bind(this, activity).
    • Bind a view's children into fields using ButterKnife.bind(this). If you use <merge> tags in a layout and inflate in a custom view constructor you can call this immediately after. Alternatively, custom view types inflated from XML can use it in the onFinishInflate() callback.

    VIEW LISTS

    You can group multiple views into a List or array.
    @BindViews({ R.id.first_name, R.id.middle_name, R.id.last_name })
    List<EditText> nameViews;
    The apply method allows you to act on all the views in a list at once.
    ButterKnife.apply(nameViews, DISABLE);
    ButterKnife.apply(nameViews, ENABLED, false);
    Action and Setter interfaces allow specifying simple behavior.
    static final ButterKnife.Action<View> DISABLE = new ButterKnife.Action<View>() {
      @Override public void apply(View view, int index) {
        view.setEnabled(false);
      }
    };
    static final ButterKnife.Setter<View, Boolean> ENABLED = new ButterKnife.Setter<View, Boolean>() {
      @Override public void set(View view, Boolean value, int index) {
        view.setEnabled(value);
      }
    };
    An Android Property can also be used with the apply method.
    ButterKnife.apply(nameViews, View.ALPHA, 0.0f);

    LISTENER BINDING

    Listeners can also automatically be configured onto methods.
    @OnClick(R.id.submit)
    public void submit(View view) {
      // TODO submit data to server...
    }
    All arguments to the listener method are optional.
    @OnClick(R.id.submit)
    public void submit() {
      // TODO submit data to server...
    }
    Define a specific type and it will automatically be cast.
    @OnClick(R.id.submit)
    public void sayHi(Button button) {
      button.setText("Hello!");
    }
    Specify multiple IDs in a single binding for common event handling.
    @OnClick({ R.id.door1, R.id.door2, R.id.door3 })
    public void pickDoor(DoorView door) {
      if (door.hasPrizeBehind()) {
        Toast.makeText(this, "You win!", LENGTH_SHORT).show();
      } else {
        Toast.makeText(this, "Try again", LENGTH_SHORT).show();
      }
    }
    Custom views can bind to their own listeners by not specifying an ID.
    public class FancyButton extends Button {
      @OnClick
      public void onClick() {
        // TODO do something!
      }
    }

    BINDING RESET

    Fragments have a different view lifecycle than activities. When binding a fragment in onCreateView, set the views to null in onDestroyView. Butter Knife returns an Unbinder instance when you call bind to do this for you. Call its unbind method in the appropriate lifecycle callback.
    public class FancyFragment extends Fragment {
      @BindView(R.id.button1) Button button1;
      @BindView(R.id.button2) Button button2;
      private Unbinder unbinder;
    
      @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fancy_fragment, container, false);
        unbinder = ButterKnife.bind(this, view);
        // TODO Use fields...
        return view;
      }
    
      @Override public void onDestroyView() {
        super.onDestroyView();
        unbinder.unbind();
      }
    }

    OPTIONAL BINDINGS

    By default, both @Bind and listener bindings are required. An exception will be thrown if the target view cannot be found.
    To suppress this behavior and create an optional binding, add a @Nullable annotation to fields or the @Optional annotation to methods.
    Note: Any annotation named @Nullable can be used for fields. It is encouraged to use the @Nullable annotation from Android's "support-annotations" library.
    @Nullable @BindView(R.id.might_not_be_there) TextView mightNotBeThere;
    
    @Optional @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {
      // TODO ...
    }

    MULTI-METHOD LISTENERS

    Method annotations whose corresponding listener has multiple callbacks can be used to bind to any one of them. Each annotation has a default callback that it binds to. Specify an alternate using the callback parameter.
    @OnItemSelected(R.id.list_view)
    void onItemSelected(int position) {
      // TODO ...
    }
    
    @OnItemSelected(value = R.id.maybe_missing, callback = NOTHING_SELECTED)
    void onNothingSelected() {
      // TODO ...
    }

    BONUS

    Also included are findById methods which simplify code that still has to find views on a ViewActivity, or Dialog. It uses generics to infer the return type and automatically performs the cast.
    View view = LayoutInflater.from(context).inflate(R.layout.thing, null);
    TextView firstName = ButterKnife.findById(view, R.id.first_name);
    TextView lastName = ButterKnife.findById(view, R.id.last_name);
    ImageView photo = ButterKnife.findById(view, R.id.photo);
    Add a static import for ButterKnife.findById and enjoy even more fun.

    Download

    GRADLE

    compile 'com.jakewharton:butterknife:8.5.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.5.1'

    License

    Copyright 2013 Jake Wharton
    
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at
    
       http://www.apache.org/licenses/LICENSE-2.0
    
    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.

    Syed Masoom Rizvi

    Author & Editor

    Hi, This is Syed Masoom Rizvi, who is continue exploring the world of programming ,programming and programming... :)

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