Tag: onClick

ClickListener on list Adapter

Add a ClickListener to a ListAdapter, in this case a RecyclerView.Adapter.

Within list Adapter class (called ItemListAdapter in this example):

    private final ListItemClickListener mOnClickListener; // Declare field for OnClickListener
    public interface ListItemClickListener { // Create custom interface for your OnClickListener
        void onListItemClick (int item);
    }
    public ItemListAdapter(int numberOfItems, ListItemClickListener listItemClickListener) { // Add as parameter to Adapter constructor
        mNumberItems = numberOfItems;
        mOnClickListener = listItemClickListener;
    }
    class NumberViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener { // In class that generates item View implement View.OnClickListener
        public NumberViewHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this); // Set an
        }
        @Override // Override onClick
        public void onClick(View v) {
            mOnClickListener.onListItemClick(getAdapterPosition()); // Call custom interface instance
        }
    }



Within Activity.


public class MainActivity extends AppCompatActivity implements ItemListAdapter.ListItemClickListener { // Implement the custom interface
        mAdapter = new ItemListAdapter(NUM_LIST_ITEMS, this); // Second parameter produces custom OnClickListener in constructor
    @Override // Override the onListItemClick from the custom interface
    public void onListItemClick(int item) {
        if (mToast != null) {
            mToast.cancel();
        }
        Context context = this;
        CharSequence text = "Item number: " + item;
        int duration = Toast.LENGTH_SHORT;
        mToast = Toast.makeText(context, text, duration);
        mToast.show();
    }
}



ud851-Exercises-student\Lesson03-Green-Recycler-View\T03.07-Exercise-RecyclerViewClickHandling

ud851-Sunshine-student\ud851-Sunshine-student\S03.02-Exercise-RecyclerViewClickHandling

ClickListener

Add a ClickListener to an item. Options 2 or 3 recommended.

Method 1 - clutters up onCreate, especially if several click events.
Does not promote code reuse.

public class AwesomeButtonActivity extends AppCompatActivity {

    private Button awesomeButton;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        awesomeButton = new Button(this);

        awesomeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                awesomeButtonClicked();
            }
        });
    }

    private void awesomeButtonClicked() {
        awesomeButton.setText("AWESOME!");
    }
}



Method 2 - Assigns OnClickListener to a field. Allows reuse.


public class AwesomeButtonActivity extends AppCompatActivity {

    private Button awesomeButton;
    
    private View.OnClickListener awesomeOnClickListener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            awesomeButtonClicked();
        }
    };

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        awesomeButton = new Button(this);

        awesomeButton.setOnClickListener(awesomeOnClickListener);
    }

    private void awesomeButtonClicked() {
        awesomeButton.setText("AWESOME!");
    }
}



Method 3 - declare a class to implement OnClickListener.

Easy to add extra functionality to e.g. count how many times clicked.


public class AwesomeButtonActivity extends AppCompatActivity {

    private Button awesomeButton;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        awesomeButton = new Button(this);

        awesomeButton.setOnClickListener(new AwesomeButtonClick());
    }

    private void awesomeButtonClicked() {
        awesomeButton.setText("AWESOME!");
    }
    
    class AwesomeButtonClick implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            awesomeButtonClicked();
        }
    }
}



Method 4 - have Activity implement OnClickListener. Gets messy with multiple click items.

Exposes onClick to anyone who has access to the Activity.

Could be problematic if other interfaces with onClick are implemented.

Does not promote code reuse.



public class AwesomeButtonActivity extends AppCompatActivity implements View.OnClickListener {

    private Button awesomeButton;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        awesomeButton = new Button(this);

        awesomeButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        awesomeButtonClicked();
    }

    private void awesomeButtonClicked() {
        awesomeButton.setText("AWESOME!");
    }
    
}