samples/training/AnimationsDemo/src/com/example/android/animationsdemo/LayoutChangesActivity.java

/*
 * Copyright 2012 The Android Open Source Project
 *
 * 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.
 */

package com.example.android.animationsdemo;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
 * This sample demonstrates how to use system-provided, automatic layout transitions. Layout
 * transitions are animations that occur when views are added to, removed from, or changed within
 * a {@link ViewGroup}.
 *
 * <p>In this sample, the user can add rows to and remove rows from a vertical
 * {@link android.widget.LinearLayout}.</p>
 */
public class LayoutChangesActivity extends Activity {
    /**
     * The container view which has layout change animations turned on. In this sample, this view
     * is a {@link android.widget.LinearLayout}.
     */
    private ViewGroup mContainerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_layout_changes);

        mContainerView = (ViewGroup) findViewById(R.id.container);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        getMenuInflater().inflate(R.menu.activity_layout_changes, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                // Navigate "up" the demo structure to the launchpad activity.
                // See http://developer.android.com/design/patterns/navigation.html for more.
                NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
                return true;

            case R.id.action_add_item:
                // Hide the "empty" view since there is now at least one item in the list.
                findViewById(android.R.id.empty).setVisibility(View.GONE);
                addItem();
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void addItem() {
        // Instantiate a new "row" view.
        final ViewGroup newView = (ViewGroup) LayoutInflater.from(this).inflate(
                R.layout.list_item_example, mContainerView, false);

        // Set the text in the new row to a random country.
        ((TextView) newView.findViewById(android.R.id.text1)).setText(
                COUNTRIES[(int) (Math.random() * COUNTRIES.length)]);

        // Set a click listener for the "X" button in the row that will remove the row.
        newView.findViewById(R.id.delete_button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // Remove the row from its parent (the container view).
                // Because mContainerView has android:animateLayoutChanges set to true,
                // this removal is automatically animated.
                mContainerView.removeView(newView);

                // If there are no rows remaining, show the empty view.
                if (mContainerView.getChildCount() == 0) {
                    findViewById(android.R.id.empty).setVisibility(View.VISIBLE);
                }
            }
        });

        // Because mContainerView has android:animateLayoutChanges set to true,
        // adding this view is automatically animated.
        mContainerView.addView(newView, 0);
    }

    /**
     * A static list of country names.
     */
    private static final String[] COUNTRIES = new String[]{
            "Belgium", "France", "Italy", "Germany", "Spain",
            "Austria", "Russia", "Poland", "Croatia", "Greece",
            "Ukraine",
    };
}