[android] Slide a layout up from bottom of screen

Here is what worked in the end for me.

Layouts:

activity_main.xml

<RelativeLayout
    android:id="@+id/main_screen"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:layout_alignParentTop="true"
    android:layout_alignParentBottom="true">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" 
        android:layout_alignParentTop="true"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world"
        android:layout_centerInParent="true" />

    <Button
        android:id="@+id/slideButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Slide up / down"
        android:layout_alignParentBottom="true" 
        android:onClick="slideUpDown"/>

</RelativeLayout>

hidden_panel.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/hidden_panel"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >
    <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Test" />
</LinearLayout>

Java: package com.example.slideuplayout;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;
import android.view.animation.Animation;
import android.view.animation.Animation.AnimationListener;
import android.view.animation.AnimationUtils;

public class MainActivity extends Activity {

private ViewGroup hiddenPanel;
private ViewGroup mainScreen;
private boolean isPanelShown;
private ViewGroup root;

int screenHeight = 0;

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

    mainScreen = (ViewGroup)findViewById(R.id.main_screen);
    ViewTreeObserver vto = mainScreen.getViewTreeObserver(); 
    vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() { 
        @Override 
        public void onGlobalLayout() { 
            screenHeight = mainScreen.getHeight();
            mainScreen.getViewTreeObserver().removeGlobalOnLayoutListener(this); 
        } 
    }); 

    root = (ViewGroup)findViewById(R.id.root);

    hiddenPanel = (ViewGroup)getLayoutInflater().inflate(R.layout.hidden_panel, root, false);
    hiddenPanel.setVisibility(View.INVISIBLE);

    root.addView(hiddenPanel);

    isPanelShown = false;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

public void slideUpDown(final View view) {
    if(!isPanelShown) {
        // Show the panel
        mainScreen.layout(mainScreen.getLeft(),
                          mainScreen.getTop() - (screenHeight * 25/100), 
                          mainScreen.getRight(),
                          mainScreen.getBottom() - (screenHeight * 25/100));



        hiddenPanel.layout(mainScreen.getLeft(), mainScreen.getBottom(), mainScreen.getRight(), screenHeight);
        hiddenPanel.setVisibility(View.VISIBLE);

        Animation bottomUp = AnimationUtils.loadAnimation(this,
                R.anim.bottom_up);

        hiddenPanel.startAnimation(bottomUp);

        isPanelShown = true;
    }
    else {
        isPanelShown = false;

        // Hide the Panel
        Animation bottomDown = AnimationUtils.loadAnimation(this,
                R.anim.bottom_down);
        bottomDown.setAnimationListener(new AnimationListener() {

            @Override
            public void onAnimationStart(Animation arg0) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onAnimationRepeat(Animation arg0) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onAnimationEnd(Animation arg0) {
                isPanelShown = false;

                mainScreen.layout(mainScreen.getLeft(),
                          mainScreen.getTop() + (screenHeight * 25/100), 
                          mainScreen.getRight(),
                          mainScreen.getBottom() + (screenHeight * 25/100));

                hiddenPanel.layout(mainScreen.getLeft(), mainScreen.getBottom(), mainScreen.getRight(), screenHeight);
            }
        });
        hiddenPanel.startAnimation(bottomDown);
    }
}
}