javaandroidresumepause
Pause/resume functionality for a game
I am a beginner with Android Studio and I don't know how this is done. My game is available from my github repo. The story is that the character is supposed to catch falling objects.
But how can I implement pause/resume functionality? How is it usually done?
My code
package dev.android.gamex;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.os.Bundle;
import android.os.Handler;
import android.os.Vibrator;
import android.support.v4.view.MotionEventCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.Window;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
CatchGame cg;
boolean pause = false;
// start app
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
cg = new CatchGame(this, 5, "Jamie");
setContentView(cg);
cg.setBackground(getResources().getDrawable(R.mipmap.jungle));
}
@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, menu);
return true;
}
// method called when top right menu is tapped
@Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
int difficulty = cg.NBRSTEPS;
String name = cg.heroName;
switch (item.getItemId()) {
case R.id.item11:
cg = new CatchGame(this, 3, name);
setContentView(cg);
return true;
case R.id.item12:
cg = new CatchGame(this, 5, name);
setContentView(cg);
return true;
case R.id.item13:
cg = new CatchGame(this, 7, name);
setContentView(cg);
return true;
case R.id.item14:
cg = new CatchGame(this, 9, name);
setContentView(cg);
return true;
case R.id.item15:
cg = new CatchGame(this, 11, name);
setContentView(cg);
return true;
case R.id.item21:
cg = new CatchGame(this, difficulty, "Jamie");
cg.setBackground(getResources().getDrawable(R.mipmap.jungle));
setContentView(cg);
return true;
case R.id.item22:
cg = new CatchGame(this, difficulty, "Spaceship");
cg.setBackground(getResources().getDrawable(R.mipmap.space));
setContentView(cg);
return true;
default:
cg.paused = true;
return super.onOptionsItemSelected(item);
}
}
}
class CatchGame extends View {
int NBRSTEPS; // number of discrete positions in the x-dimension; must be uneven
String heroName;
int screenW;
int screenH;
int[] x; // x-coordinates for falling objects
int[] y; // y-coordinates for falling objects
int[] hero_positions; // x-coordinates for hero
Random random = new Random();
int ballW; // width of each falling object
int ballH; // height of ditto
float dY; //vertical speed
Bitmap ball, hero;
int heroXCoord;
int heroYCoord;
int xsteps;
int score;
int offset;
boolean gameOver; // default value is false
boolean toastDisplayed;
boolean paused = false;
// constructor, load images and get sizes
public CatchGame(Context context, int difficulty, String name) {
super(context);
NBRSTEPS = difficulty;
heroName = name;
x = new int[NBRSTEPS];
y = new int[NBRSTEPS];
hero_positions = new int[NBRSTEPS];
int resourceIdFalling = 0;
int resourceIdHero = 0;
if (heroName.equals("Jamie")) {
resourceIdFalling = R.mipmap.falling_object2;
resourceIdHero = R.mipmap.jamie;
}
if (heroName.equals("Spaceship")) {
resourceIdFalling = R.mipmap.falling_object;
resourceIdHero = R.mipmap.ufo;
}
ball = BitmapFactory.decodeResource(getResources(), resourceIdFalling); //load a ball image
hero = BitmapFactory.decodeResource(getResources(), resourceIdHero); //load a hero image
ballW = ball.getWidth();
ballH = ball.getHeight();
}
// set coordinates, etc.
void initialize() {
if (!gameOver) { // run only once, when the game is first started
int maxOffset = (NBRSTEPS - 1) / 2;
for (int i = 0; i < x.length; i++) {
int origin = (screenW / 2) + xsteps * (i - maxOffset);
x[i] = origin - (ballW / 2);
hero_positions[i] = origin - hero.getWidth();
}
int heroWidth = hero.getWidth();
int heroHeight = hero.getHeight();
hero = Bitmap.createScaledBitmap(hero, heroWidth * 2, heroHeight * 2, true);
heroYCoord = screenH - 2 * heroHeight; // bottom of screen
}
for (int i = 0; i < y.length; i++) {
y[i] = -random.nextInt(1000); // place items randomly in vertical direction
}
offset = (NBRSTEPS - 1) / 2; // place hero at centre of the screen
heroXCoord = hero_positions[offset];
// initialize or reset global attributes
dY = 2.0f;
score = 0;
gameOver = false;
toastDisplayed = false;
}
// method called when the screen opens
@Override
public void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
screenW = w;
screenH = h;
xsteps = w / NBRSTEPS;
initialize();
}
// method called when the "game over" toast has finished displaying
void restart(Canvas canvas) {
toastDisplayed = true;
initialize();
draw(canvas);
}
// update the canvas in order to display the game action
@Override
public void onDraw(Canvas canvas) {
if (toastDisplayed) {
restart(canvas);
return;
}
super.onDraw(canvas);
int heroHeight = hero.getHeight();
int heroWidth = hero.getWidth();
int heroCentre = heroXCoord + heroWidth / 2;
Context context = this.getContext();
// compute locations of falling objects
for (int i = 0; i < y.length; i++) {
if (!paused) {
y[i] += (int) dY;
}
// if falling object hits bottom of screen
if (y[i] > (screenH - ballH) && !gameOver) {
dY = 0;
gameOver = true;
paused = true;
int duration = Toast.LENGTH_SHORT;
final Toast toast = Toast.makeText(context, "GAME OVER!\nScore: " + score, duration);
toast.show();
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
toast.cancel();
toastDisplayed = true;
}
}, 3000);
//Vibrator v = (Vibrator) context.getSystemService(context.VIBRATOR_SERVICE);
// Vibrate for 3000 milliseconds
//v.vibrate(3000);
}
// if the hero catches a falling object
if (x[i] < heroCentre && x[i] + ballW > heroCentre &&
y[i] > screenH - ballH - heroHeight) {
y[i] = -random.nextInt(1000); // reset to new vertical position
score += 1;
}
LinearLayout layout = new LinearLayout(this.getContext());
TextView textView = new TextView(context);
textView.setVisibility(View.VISIBLE);
String str = "Score: " + score;
textView.setText(str);
layout.addView(textView);
layout.measure(canvas.getWidth(), canvas.getHeight());
layout.layout(0, 0, canvas.getWidth(), canvas.getHeight());
layout.draw(canvas);
}
canvas.save(); //Save the position of the canvas.
for (int i = 0; i < y.length; i++) {
canvas.drawBitmap(ball, x[i], y[i], null); //Draw the ball on the canvas.
}
canvas.drawBitmap(hero, heroXCoord, heroYCoord, null); //Draw the hero on the canvas.
canvas.restore();
//Call the next frame.
invalidate();
}
// event listener for when the user touches the screen
@Override
public boolean onTouchEvent(MotionEvent event) {
if (paused) {
paused = false;
}
int action = MotionEventCompat.getActionMasked(event);
if (action != MotionEvent.ACTION_DOWN || gameOver) { // non-touchdown event or gameover
return true; // do nothing
}
int coordX = (int) event.getX();
int xCentre = (screenW / 2) - (hero.getWidth() / 2);
int maxOffset = hero_positions.length - 1; // can't move outside right edge of screen
int minOffset = 0; // ditto left edge of screen
if (coordX < xCentre && offset > minOffset) { // touch event left of the centre of screen
offset--; // move hero to the left
}
if (coordX > xCentre && offset < maxOffset) { // touch event right of the centre of screen
offset++; // move hero to the right
}
heroXCoord = hero_positions[offset];
return true;
}
}
Solution
Nice game!
- You already implemented
pausefunctionality, so I just used it. - Add view inside of
onDraw()is very bad, because it makes app too slow. So keep heavy jobs outside ofonDraw(). For update score, I add new interfaceOnScoreListener. - And, I added Pause / Play button.
Code is:
package dev.android.gamex;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.support.v4.view.MotionEventCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
CatchGame cg;
public TextView textView;
// start app
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout mainLayout = new LinearLayout(this);
mainLayout.setOrientation(LinearLayout.VERTICAL);
LinearLayout menuLayout = new LinearLayout(this);
menuLayout.setBackgroundColor(Color.parseColor("#FFFFFF"));
textView = new TextView(this);
textView.setVisibility(View.VISIBLE);
String str = "Score: 0";
textView.setText(str);
menuLayout.addView(textView);
Button button = new Button(this);
button.setText("Pause");
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
togglePausePlay();
}
});
menuLayout.addView(button);
mainLayout.addView(menuLayout);
cg = new CatchGame(this, 5, "Jamie", onScoreListener);
cg.setBackground(getResources().getDrawable(R.mipmap.jungle));
mainLayout.addView(cg);
setContentView(mainLayout);
}
private void togglePausePlay() {
if (cg.paused) {
// play
Toast.makeText(MainActivity.this, "Play", Toast.LENGTH_SHORT).show();
} else {
// pause
Toast.makeText(MainActivity.this, "Pause", Toast.LENGTH_SHORT).show();
}
cg.paused = !cg.paused;
}
private OnScoreListener onScoreListener = new OnScoreListener() {
@Override
public void onScore(int score) {
textView.setText("Score: " + score);
}
};
@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, menu);
return true;
}
// method called when top right menu is tapped
@Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
int difficulty = cg.NBRSTEPS;
String name = cg.heroName;
switch (item.getItemId()) {
case R.id.item11:
cg = new CatchGame(this, 3, name, onScoreListener);
setContentView(cg);
return true;
case R.id.item12:
cg = new CatchGame(this, 5, name, onScoreListener);
setContentView(cg);
return true;
case R.id.item13:
cg = new CatchGame(this, 7, name, onScoreListener);
setContentView(cg);
return true;
case R.id.item14:
cg = new CatchGame(this, 9, name, onScoreListener);
setContentView(cg);
return true;
case R.id.item15:
cg = new CatchGame(this, 11, name, onScoreListener);
setContentView(cg);
return true;
case R.id.item21:
cg = new CatchGame(this, difficulty, "Jamie", onScoreListener);
cg.setBackground(getResources().getDrawable(R.mipmap.jungle));
setContentView(cg);
return true;
case R.id.item22:
cg = new CatchGame(this, difficulty, "Spaceship", onScoreListener);
cg.setBackground(getResources().getDrawable(R.mipmap.space));
setContentView(cg);
return true;
default:
cg.paused = true;
return super.onOptionsItemSelected(item);
}
}
}
interface OnScoreListener {
void onScore(int score);
}
class CatchGame extends View {
int NBRSTEPS; // number of discrete positions in the x-dimension; must be uneven
String heroName;
int screenW;
int screenH;
int[] x; // x-coordinates for falling objects
int[] y; // y-coordinates for falling objects
int[] hero_positions; // x-coordinates for hero
Random random = new Random();
int ballW; // width of each falling object
int ballH; // height of ditto
float dY; //vertical speed
Bitmap ball, hero;
int heroXCoord;
int heroYCoord;
int xsteps;
int score;
int offset;
boolean gameOver; // default value is false
boolean toastDisplayed;
boolean paused = false;
OnScoreListener onScoreListener;
// constructor, load images and get sizes
public CatchGame(Context context, int difficulty, String name, OnScoreListener onScoreListener) {
super(context);
NBRSTEPS = difficulty;
heroName = name;
this.onScoreListener = onScoreListener;
x = new int[NBRSTEPS];
y = new int[NBRSTEPS];
hero_positions = new int[NBRSTEPS];
int resourceIdFalling = 0;
int resourceIdHero = 0;
if (heroName.equals("Jamie")) {
resourceIdFalling = R.mipmap.falling_object2;
resourceIdHero = R.mipmap.jamie;
}
if (heroName.equals("Spaceship")) {
resourceIdFalling = R.mipmap.falling_object;
resourceIdHero = R.mipmap.ufo;
}
ball = BitmapFactory.decodeResource(getResources(), resourceIdFalling); //load a ball image
hero = BitmapFactory.decodeResource(getResources(), resourceIdHero); //load a hero image
ballW = ball.getWidth();
ballH = ball.getHeight();
}
// set coordinates, etc.
void initialize() {
if (!gameOver) { // run only once, when the game is first started
int maxOffset = (NBRSTEPS - 1) / 2;
for (int i = 0; i < x.length; i++) {
int origin = (screenW / 2) + xsteps * (i - maxOffset);
x[i] = origin - (ballW / 2);
hero_positions[i] = origin - hero.getWidth();
}
int heroWidth = hero.getWidth();
int heroHeight = hero.getHeight();
hero = Bitmap.createScaledBitmap(hero, heroWidth * 2, heroHeight * 2, true);
heroYCoord = screenH - 2 * heroHeight; // bottom of screen
}
for (int i = 0; i < y.length; i++) {
y[i] = -random.nextInt(1000); // place items randomly in vertical direction
}
offset = (NBRSTEPS - 1) / 2; // place hero at centre of the screen
heroXCoord = hero_positions[offset];
// initialize or reset global attributes
dY = 2.0f;
score = 0;
gameOver = false;
toastDisplayed = false;
}
// method called when the screen opens
@Override
public void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
screenW = w;
screenH = h;
xsteps = w / NBRSTEPS;
initialize();
}
// method called when the "game over" toast has finished displaying
void restart(Canvas canvas) {
toastDisplayed = true;
initialize();
draw(canvas);
}
// update the canvas in order to display the game action
@Override
public void onDraw(Canvas canvas) {
if (toastDisplayed) {
restart(canvas);
return;
}
super.onDraw(canvas);
int heroHeight = hero.getHeight();
int heroWidth = hero.getWidth();
int heroCentre = heroXCoord + heroWidth / 2;
Context context = this.getContext();
// compute locations of falling objects
for (int i = 0; i < y.length; i++) {
if (!paused) {
y[i] += (int) dY;
}
// if falling object hits bottom of screen
if (y[i] > (screenH - ballH) && !gameOver) {
dY = 0;
gameOver = true;
paused = true;
int duration = Toast.LENGTH_SHORT;
final Toast toast = Toast.makeText(context, "GAME OVER!\nScore: " + score, duration);
toast.show();
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
toast.cancel();
toastDisplayed = true;
}
}, 3000);
//Vibrator v = (Vibrator) context.getSystemService(context.VIBRATOR_SERVICE);
// Vibrate for 3000 milliseconds
//v.vibrate(3000);
}
// if the hero catches a falling object
if (x[i] < heroCentre && x[i] + ballW > heroCentre &&
y[i] > screenH - ballH - heroHeight) {
y[i] = -random.nextInt(1000); // reset to new vertical position
score += 1;
onScoreListener.onScore(score);
}
}
canvas.save(); //Save the position of the canvas.
for (int i = 0; i < y.length; i++) {
canvas.drawBitmap(ball, x[i], y[i], null); //Draw the ball on the canvas.
}
canvas.drawBitmap(hero, heroXCoord, heroYCoord, null); //Draw the hero on the canvas.
canvas.restore();
//Call the next frame.
invalidate();
}
// event listener for when the user touches the screen
@Override
public boolean onTouchEvent(MotionEvent event) {
if (paused) {
paused = false;
}
int action = MotionEventCompat.getActionMasked(event);
if (action != MotionEvent.ACTION_DOWN || gameOver) { // non-touchdown event or gameover
return true; // do nothing
}
int coordX = (int) event.getX();
int xCentre = (screenW / 2) - (hero.getWidth() / 2);
int maxOffset = hero_positions.length - 1; // can't move outside right edge of screen
int minOffset = 0; // ditto left edge of screen
if (coordX < xCentre && offset > minOffset) { // touch event left of the centre of screen
offset--; // move hero to the left
}
if (coordX > xCentre && offset < maxOffset) { // touch event right of the centre of screen
offset++; // move hero to the right
}
heroXCoord = hero_positions[offset];
return true;
}
}
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