Game development - how to?

Question

I am creating a game and I have assigned three image views of (balls) at the top of my screen and code an animation for them. The balls are going down to the bottom from the top, but I want the balls from the top of the screen to not show at the start of the animation... any advice?

Here is the relevant Activity code:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ball1 = (ImageView) findViewById(R.id.ball1);
        ball2 = (ImageView) findViewById(R.id.ball2);
        ball3 = (ImageView) findViewById(R.id.ball3);  

    }

private void startBallAnimation() {
    final TranslateAnimation animation = new TranslateAnimation(
            TranslateAnimation.RELATIVE_TO_PARENT, 0.0f,
            TranslateAnimation.RELATIVE_TO_PARENT, 0.0f,
            TranslateAnimation.RELATIVE_TO_PARENT, 0.0f,
            TranslateAnimation.RELATIVE_TO_PARENT, 0.86f
    );

    animation.setAnimationListener(new Animation.AnimationListener() {
        @Override
        public void onAnimationStart(Animation animation) {
            mhandle.post(new Runnable() {
                @Override
                public void run() {
                    setBallColors();
                }
            });
        }

        @Override
        public void onAnimationRepeat(Animation animation) {}

        @Override
        public void onAnimationEnd(final Animation animation) {}

    }
}

Here is my XML:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFFFFF"
    tools:context="com.example.hp.colorspoof.MainActivity">

    <!-- ball imageviews -->
    <ImageView
        android:id="@+id/ball1"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_gravity="left"
        android:layout_marginLeft="40dp"
        app:srcCompat="@drawable/ball_0" />

    <ImageView
        android:id="@+id/ball2"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_gravity="center_horizontal"
        app:srcCompat="@drawable/row2_2" />

    <ImageView
        android:id="@+id/ball3"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_gravity="right"
        android:layout_marginRight="40dp"
        app:srcCompat="@drawable/row3_1" />
</FrameLayout>

Answer 1

Below is a simple untested implementation of what you want to do. I unfortunately no longer have an environment for programming Android setup, so I can't test the code for you, but this should work.

Please note that I made use of negative margins because that is the easiest way to implement it, but it isn't necessarily the best way to achieve it. See here for more: Is it a bad practice to use negative margins in Android?

To provide a summary of the changes in the XML below from what you provided:

1. I provided a RelativeLayout to contain your playfield. It's generally a good practice to include a FrameLayout at the top level and then use a RelativeLayout or LinearLayout below it to contain the views that will need to be manipulated. RelativeLayout and LinearLayout provide good means of placing views in relation to each other. There is also a newer type of Layout called the ConstraintLayout that I'm not personally familiar with but you may want to look at instead of RelativeLayout. See more here: What are the differences between LinearLayout, RelativeLayout, and AbsoluteLayout?
2. I removed the android:layout_gravity statements. You don't need those with a RelativeLayout.
3. I utilized android:layout_alignParentTop and android:layout_marginTop to place the balls above the top of your layout by exactly the size of the ball.
4. I utilized android:layout_marginLeft, android:layout_centerHorizontal, and android:layout_marginRight to place the balls horizontally on the screen as you did.

XML below:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFFFFF"
    tools:context="com.example.hp.colorspoof.MainActivity">

    <RelativeLayout
        android:id="@+id/play_area"
        android:layout_width="match_parent"
        android:layout_height"match_parent">

        <!-- ball imageviews -->
        <ImageView
            android:id="@+id/ball1"
            android:layout_width="30dp"
            android:layout_height="30dp"
            android:layout_alignParentTop="true"
            android:layout_marginTop="-30dp"
            android:layout_marginLeft="40dp"
            app:srcCompat="@drawable/ball_0" />

        <ImageView
            android:id="@+id/ball2"
            android:layout_width="30dp"
            android:layout_height="30dp"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="-30dp"
            app:srcCompat="@drawable/row2_2" />

        <ImageView
            android:id="@+id/ball3"
            android:layout_width="30dp"
            android:layout_height="30dp"
            android:layout_alignParentTop="true"
            android:layout_alignParentRight="true"
            android:layout_marginTop="-30dp"
            android:layout_marginRight="40dp"
            app:srcCompat="@drawable/row3_1" />

    </RelativeLayout>

</FrameLayout>