An implementation of a "findViewsByTag" method on Android

strings.xml

<resources>

    <string name="tag">tag:touchMe</string>
    <string name="touch_me">Touch me!</string>

</resources>

ViewAdditions.java

package com.cyrilmottier.android.tests;

import android.view.View;
import android.view.ViewGroup;

/**
 * @author Cyril Mottier
 */
public class ViewAdditions {

    public interface OnTagFoundHandler {
        void onTagFound(View v);
    }

    public static final void findViewsByTag(View root, String tag, OnTagFoundHandler handler) {
        if (root == null) {
            throw new NullPointerException();
        }
        if (tag == null || handler == null) {
            return;
        }
        if (tag.equals(root.getTag())) {
            handler.onTagFound(root);
        }
        if (root instanceof ViewGroup) {
            final ViewGroup rootGroup = (ViewGroup) root;
            final int childCount = rootGroup.getChildCount();
            for (int i = 0; i < childCount; i++) {
                findViewsByTag(rootGroup.getChildAt(i), tag, handler);
            }
        }
    }

}

ViewAdditionsActivity.java

package com.cyrilmottier.android.tests;

import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.Toast;

import com.cyrilmottier.android.tests.ViewAdditions.OnTagFoundHandler;

/**
 * @author Cyril Mottier
 */
public class ViewAdditionsActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.view_additions_activity);

        ViewAdditions.findViewsByTag(findViewById(R.id.root), getString(R.string.tag), new OnTagFoundHandler() {
            @Override
            public void onTagFound(View v) {
                v.setOnTouchListener(mOnTouchListener);
            }
        });
    }

    private OnTouchListener mOnTouchListener = new OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    Toast.makeText(getApplicationContext(), "ACTION_DOWN fired", Toast.LENGTH_SHORT).show();
                    break;
            }
            return true;
        }
    };

}

views_additions_activity.xml

<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/root"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:columnCount="2"
    android:useDefaultMargins="true" >

    <TextView
        android:background="#dedede"
        android:ellipsize="end"
        android:gravity="center"
        android:padding="16dp"
        android:tag="@string/tag"
        android:text="@string/touch_me" />

    <TextView
        android:background="#dedede"
        android:ellipsize="end"
        android:gravity="center"
        android:padding="16dp"
        android:tag="@string/tag"
        android:text="@string/touch_me" />

    <TextView
        android:background="#dedede"
        android:ellipsize="end"
        android:gravity="center"
        android:padding="16dp"
        android:tag="@string/tag"
        android:text="@string/touch_me" />

    <TextView
        android:background="#dedede"
        android:ellipsize="end"
        android:gravity="center"
        android:padding="16dp"
        android:tag="@string/tag"
        android:text="@string/touch_me" />

</GridLayout>