This is a fairly substantial application that we worked through in class, to create a random selection of images on cards for a memory game.
You’ll need files in res/drawable-mdpi named card1.png, card2.png, etc. I used 64×64 pixel images from Gravatar: http://www.gravatar.com/avatar/205e460b4fff2e5b48aec07710c08d50?s=64&d=retro where you can change any hex digits you want in that long code (205…d50) to generate different ones.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Easy Game"
android:id="@+id/easyB" android:layout_gravity="center"
android:onClick="selectLevel"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Medium Game"
android:id="@+id/mediumB" android:layout_gravity="center"
android:onClick="selectLevel"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Difficult Game"
android:id="@+id/difficultB" android:layout_gravity="center"
android:onClick="selectLevel"/>
</LinearLayout>package com.example.memory;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
public class MenuActivity extends Activity {
static String GAME_LEVEL_KEY = "SelectedLevel";
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.menu);
}
public void selectLevel(View v) {
Intent i = new Intent(this, GameActivity.class);
switch(v.getId()) {
case R.id.easyB:
i.putExtra(GAME_LEVEL_KEY, 1);
break;
case R.id.mediumB:
i.putExtra(GAME_LEVEL_KEY, 2);
break;
case R.id.difficultB:
i.putExtra(GAME_LEVEL_KEY, 3);
break;
}
startActivity(i);
}
}<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Hello World, GameActivity"
android:id="@+id/textView" android:textSize="32dp"/>
<GridLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center" android:rowCount="3"
android:columnCount="3" android:id="@+id/grid">
</GridLayout>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Shuffle"
android:id="@+id/shuffle" android:layout_gravity="center"
android:onClick="clickShuffle"/>
</LinearLayout>package com.example.memory;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.GridLayout;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.Random;
public class GameActivity extends Activity {
// The "value" (image) on each card, or -1 if unknown or blank.
int NUM_CARDS;
int[] cards;
TextView helloText;
int NUM_IMAGES = 13;
boolean[] used = new boolean[NUM_IMAGES];
Random rng = new Random();
GridLayout grid;
int[] drawables = {
R.drawable.card1,
R.drawable.card2,
R.drawable.card3,
R.drawable.card4,
R.drawable.card5,
R.drawable.card6,
R.drawable.card7,
R.drawable.card8,
R.drawable.card9,
R.drawable.card10,
R.drawable.card11,
R.drawable.card12,
R.drawable.card13
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Read the parameter
int level = getIntent().getIntExtra(MenuActivity.GAME_LEVEL_KEY, 1);
int size = level+2; // 1->3x3, 2->4x4, 3->5x5
NUM_CARDS = size*size; // 9 16 25
cards = new int[NUM_CARDS];
grid = (GridLayout) findViewById(R.id.grid);
grid.setRowCount(size);
grid.setColumnCount(size);
// Embed the image views in each location
for(int i = 0; i < NUM_CARDS; i++) {
grid.addView(new ImageView(this), i);
}
helloText = (TextView) findViewById(R.id.textView);
helloText.setText("Welcome to level " + level);
shuffleCards();
}
public void showCards() {
// Display array in text view to help debug
String buf = "";
for(int i = 0; i < NUM_CARDS; i++) {
buf += cards[i] + " ";
}
helloText.setText(buf);
// Put the images in the GridLayout.
for(int i = 0; i < NUM_CARDS; i++) {
ImageView v = (ImageView) grid.getChildAt(i);
v.setImageResource(drawables[cards[i]]);
}
}
public void clickShuffle(View v) {
shuffleCards();
}
public int chooseUnusedLocation() {
int loc = rng.nextInt(NUM_CARDS);
while(cards[loc] != -1) {
loc = rng.nextInt(NUM_CARDS); // Try again
}
return loc;
}
public int chooseUnusedImage() {
int im = rng.nextInt(NUM_IMAGES);
while(used[im]) { // Already used, try again
im = rng.nextInt(NUM_IMAGES);
}
used[im] = true;
return im;
}
public void shuffleCards() {
// First set all to unknown.
for(int i = 0; i < NUM_CARDS; i++) {
cards[i] = -1;
}
// Start with all images unused
for(int i = 0; i < NUM_IMAGES; i++) {
used[i] = false;
}
// For each pair
for(int i = 0; i < NUM_CARDS / 2; i++) {
// Choose a random image
int im = chooseUnusedImage();
int loc1 = chooseUnusedLocation();
cards[loc1] = im;
int loc2 = chooseUnusedLocation();
cards[loc2] = im;
}
// There might be one remaining card (if NUM_CARDS was odd)
// we have to fill with an image.
for(int i = 0; i < NUM_CARDS; i++) {
if(cards[i] == -1) {
cards[i] = chooseUnusedImage();
}
}
showCards();
}
}