我试图修改Snake游戏代码以触发以下声音：
我认为代码与GitHub上提供的代码相同或几乎相同。我尝试使用MediaPlayer类为每个声音创建一个MediaPlayer对象：
MediaPlayer mpOver = new MediaPlayer();
然后通过以下方式将对象设置为原始文件：
mpOver.create(Snake.this, R.raw.bump);
然后通过以下方法触发声音：
mpOver.start();
但是，我只能在Snake类的onCreate方法中使用它。
截至目前，我只有一个MediaPlayer对象被声明为mpOver。当蛇从一块瓷砖移动到另一块瓷砖时，最终会发出声音。我在onCreate方法的Snake类中使用它的原因只是为了测试我是否可以让它发出声音，它在启动时会发出声音。我只是不知道如何将它发送到其余部分该应用程序。有人可以提供任何建议吗？
Snake类的更新代码如下：
感谢您的帮助，我仍然遇到问题。我使用了你的代码，它运行良好，没有音频，直到我添加
MediaPlayer mpOver = activity.getMpOver();
mpOver.start();
当调用应该播放声音的方法时，应用程序崩溃了。
我在android监视器中收到此错误：
02-15 09:25:51.576 4163-4163 / com.example.android.snake E / AndroidRuntime：FATAL EXCEPTION：main 处理：com.example.android.snake，PID：4163 java.lang.NullPointerException：尝试调用虚方法＆＃39; void android.media.MediaPlayer.start（）＆＃39;在null对象引用上 在com.example.android.snake.SnakeView.updateSnake（SnakeView.java:501） 在com.example.android.snake.SnakeView.update（SnakeView.java:427） 在com.example.android.snake.SnakeView $ RefreshHandler.handleMessage（SnakeView.java:131） 在android.os.Handler.dispatchMessage（Handler.java:102） 在android.os.Looper.loop（Looper.java:148） 在android.app.ActivityThread.main（ActivityThread.java:5417） at java.lang.reflect.Method.invoke（Native Method） 在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:726） 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616）
抱歉，我的更新代码低于......并且非常感谢您的帮助。
package com.example.android.snake;
import android.content.Context;
import android.content.res.Resources;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.Random;
/**
* SnakeView: implementation of a simple game of Snake
*
*
*/
public class SnakeView extends TileView {
private static final String TAG = "SnakeView";
private Snake activity;
public void setActivity(Snake activity) {
this.activity = activity;
}
/**
* Current mode of application: READY to run, RUNNING, or you have already
* lost. static final ints are used instead of an enum for performance
* reasons.
*/
private int mMode = READY;
public static final int PAUSE = 0;
public static final int READY = 1;
public static final int RUNNING = 2;
public static final int LOSE = 3;
/**
* Current direction the snake is headed.
*/
private int mDirection = NORTH;
private int mNextDirection = NORTH;
private static final int NORTH = 1;
private static final int SOUTH = 2;
private static final int EAST = 3;
private static final int WEST = 4;
/**
* Labels for the drawables that will be loaded into the TileView class
*/
private static final int RED_STAR = 1;
private static final int YELLOW_STAR = 2;
private static final int GREEN_STAR = 3;
/**
* mScore: used to track the number of apples captured mMoveDelay: number of
* milliseconds between snake movements. This will decrease as apples are
* captured.
*/
private long mScore = 0;
private long mMoveDelay = 600;
/**
* mLastMove: tracks the absolute time when the snake last moved, and is used
* to determine if a move should be made based on mMoveDelay.
*/
private long mLastMove;
/**
* mStatusText: text shows to the user in some run states
*/
private TextView mStatusText;
/**
* mSnakeTrail: a list of Coordinates that make up the snake's body
* mAppleList: the secret location of the juicy apples the snake craves.
*/
private ArrayList<Coordinate> mSnakeTrail = new ArrayList<Coordinate>();
private ArrayList<Coordinate> mAppleList = new ArrayList<Coordinate>();
/**
* Everyone needs a little randomness in their life
*/
private static final Random RNG = new Random();
/**
* Create a simple handler that we can use to cause animation to happen. We
* set ourselves as a target and we can use the sleep()
* function to cause an update/invalidate to occur at a later date.
*/
private RefreshHandler mRedrawHandler = new RefreshHandler();
class RefreshHandler extends Handler {
@Override
public void handleMessage(Message msg) {
SnakeView.this.update();
SnakeView.this.invalidate();
}
public void sleep(long delayMillis) {
this.removeMessages(0);
sendMessageDelayed(obtainMessage(0), delayMillis);
}
};
/**
* Constructs a SnakeView based on inflation from XML
*
* @param context
* @param attrs
*/
public SnakeView(Context context, AttributeSet attrs) {
super(context, attrs);
initSnakeView();
}
public SnakeView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initSnakeView();
}
private void initSnakeView() {
setFocusable(true);
Resources r = this.getContext().getResources();
resetTiles(4);
loadTile(RED_STAR, r.getDrawable(R.drawable.redstar));
loadTile(YELLOW_STAR, r.getDrawable(R.drawable.yellowstar));
loadTile(GREEN_STAR, r.getDrawable(R.drawable.greenstar));
}
private void initNewGame() {
mSnakeTrail.clear();
mAppleList.clear();
// For now we're just going to load up a short default eastbound snake
// that's just turned north
mSnakeTrail.add(new Coordinate(7, 7));
mSnakeTrail.add(new Coordinate(6, 7));
mSnakeTrail.add(new Coordinate(5, 7));
mSnakeTrail.add(new Coordinate(4, 7));
mSnakeTrail.add(new Coordinate(3, 7));
mSnakeTrail.add(new Coordinate(2, 7));
mNextDirection = NORTH;
// Two apples to start with
addRandomApple();
addRandomApple();
mMoveDelay = 600;
mScore = 0;
}
/**
* Given a ArrayList of coordinates, we need to flatten them into an array of
* ints before we can stuff them into a map for flattening and storage.
*
* @param cvec : a ArrayList of Coordinate objects
* @return : a simple array containing the x/y values of the coordinates
* as [x1,y1,x2,y2,x3,y3...]
*/
private int[] coordArrayListToArray(ArrayList<Coordinate> cvec) {
int count = cvec.size();
int[] rawArray = new int[count * 2];
for (int index = 0; index < count; index++) {
Coordinate c = cvec.get(index);
rawArray[2 * index] = c.x;
rawArray[2 * index + 1] = c.y;
}
return rawArray;
}
/**
* Save game state so that the user does not lose anything
* if the game process is killed while we are in the
* background.
*
* @return a Bundle with this view's state
*/
public Bundle saveState() {
Bundle map = new Bundle();
map.putIntArray("mAppleList", coordArrayListToArray(mAppleList));
map.putInt("mDirection", Integer.valueOf(mDirection));
map.putInt("mNextDirection", Integer.valueOf(mNextDirection));
map.putLong("mMoveDelay", Long.valueOf(mMoveDelay));
map.putLong("mScore", Long.valueOf(mScore));
map.putIntArray("mSnakeTrail", coordArrayListToArray(mSnakeTrail));
return map;
}
/**
* Given a flattened array of ordinate pairs, we reconstitute them into a
* ArrayList of Coordinate objects
*
* @param rawArray : [x1,y1,x2,y2,...]
* @return a ArrayList of Coordinates
*/
private ArrayList<Coordinate> coordArrayToArrayList(int[] rawArray) {
ArrayList<Coordinate> coordArrayList = new ArrayList<Coordinate>();
int coordCount = rawArray.length;
for (int index = 0; index < coordCount; index += 2) {
Coordinate c = new Coordinate(rawArray[index], rawArray[index + 1]);
coordArrayList.add(c);
}
return coordArrayList;
}
/**
* Restore game state if our process is being relaunched
*
* @param icicle a Bundle containing the game state
*/
public void restoreState(Bundle icicle) {
setMode(PAUSE);
mAppleList = coordArrayToArrayList(icicle.getIntArray("mAppleList"));
mDirection = icicle.getInt("mDirection");
mNextDirection = icicle.getInt("mNextDirection");
mMoveDelay = icicle.getLong("mMoveDelay");
mScore = icicle.getLong("mScore");
mSnakeTrail = coordArrayToArrayList(icicle.getIntArray("mSnakeTrail"));
}
/*
* handles key events in the game. Update the direction our snake is traveling
* based on the DPAD. Ignore events that would cause the snake to immediately
* turn back on itself.
*
* (non-Javadoc)
*
* @see android.view.View#onKeyDown(int, android.os.KeyEvent)
*/
@Override
public boolean onKeyDown(int keyCode, KeyEvent msg) {
if (keyCode == KeyEvent.KEYCODE_DPAD_UP) {
if (mMode == READY | mMode == LOSE) {
/*
* At the beginning of the game, or the end of a previous one,
* we should start a new game.
*/
initNewGame();
setMode(RUNNING);
update();
return (true);
}
if (mMode == PAUSE) {
/*
* If the game is merely paused, we should just continue where
* we left off.
*/
setMode(RUNNING);
update();
return (true);
}
if (mDirection != SOUTH) {
mNextDirection = NORTH;
}
return (true);
}
if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN) {
if (mDirection != NORTH) {
mNextDirection = SOUTH;
}
return (true);
}
if (keyCode == KeyEvent.KEYCODE_DPAD_LEFT) {
if (mDirection != EAST) {
mNextDirection = WEST;
}
return (true);
}
if (keyCode == KeyEvent.KEYCODE_DPAD_RIGHT) {
if (mDirection != WEST) {
mNextDirection = EAST;
}
return (true);
}
return super.onKeyDown(keyCode, msg);
}
/**
* Sets the TextView that will be used to give information (such as "Game
* Over" to the user.
*
* @param newView
*/
public void setTextView(TextView newView) {
mStatusText = newView;
}
/**
* Updates the current mode of the application (RUNNING or PAUSED or the like)
* as well as sets the visibility of textview for notification
*
* @param newMode
*/
public void setMode(int newMode) {
int oldMode = mMode;
mMode = newMode;
if (newMode == RUNNING & oldMode != RUNNING) {
mStatusText.setVisibility(View.INVISIBLE);
update();
return;
}
Resources res = getContext().getResources();
CharSequence str = "";
if (newMode == PAUSE) {
str = res.getText(R.string.mode_pause);
}
if (newMode == READY) {
str = res.getText(R.string.mode_ready);
}
if (newMode == LOSE) {
str = res.getString(R.string.mode_lose_prefix) + mScore
+ res.getString(R.string.mode_lose_suffix);
}
mStatusText.setText(str);
mStatusText.setVisibility(View.VISIBLE);
}
/**
* Selects a random location within the garden that is not currently covered
* by the snake. Currently _could_ go into an infinite loop if the snake
* currently fills the garden, but we'll leave discovery of this prize to a
* truly excellent snake-player.
*
*/
private void addRandomApple() {
Coordinate newCoord = null;
boolean found = false;
while (!found) {
// Choose a new location for our apple
int newX = 1 + RNG.nextInt(mXTileCount - 2);
int newY = 1 + RNG.nextInt(mYTileCount - 2);
newCoord = new Coordinate(newX, newY);
// Make sure it's not already under the snake
boolean collision = false;
int snakelength = mSnakeTrail.size();
for (int index = 0; index < snakelength; index++) {
if (mSnakeTrail.get(index).equals(newCoord)) {
collision = true;
}
}
// if we're here and there's been no collision, then we have
// a good location for an apple. Otherwise, we'll circle back
// and try again
found = !collision;
}
if (newCoord == null) {
Log.e(TAG, "Somehow ended up with a null newCoord!");
}
mAppleList.add(newCoord);
}
/**
* Handles the basic update loop, checking to see if we are in the running
* state, determining if a move should be made, updating the snake's location.
*/
public void update() {
if (mMode == RUNNING) {
long now = System.currentTimeMillis();
if (now - mLastMove > mMoveDelay) {
clearTiles();
updateWalls();
updateSnake();
updateApples();
mLastMove = now;
}
mRedrawHandler.sleep(mMoveDelay);
}
}
/**
* Draws some walls.
*
*/
private void updateWalls() {
for (int x = 0; x < mXTileCount; x++) {
setTile(GREEN_STAR, x, 0);
setTile(GREEN_STAR, x, mYTileCount - 1);
}
for (int y = 1; y < mYTileCount - 1; y++) {
setTile(GREEN_STAR, 0, y);
setTile(GREEN_STAR, mXTileCount - 1, y);
}
}
/**
* Draws some apples.
*
*/
private void updateApples() {
for (Coordinate c : mAppleList) {
setTile(YELLOW_STAR, c.x, c.y);
}
}
/**
* Figure out which way the snake is going, see if he's run into anything (the
* walls, himself, or an apple). If he's not going to die, we then add to the
* front and subtract from the rear in order to simulate motion. If we want to
* grow him, we don't subtract from the rear.
*
*/
private void updateSnake() {
boolean growSnake = false;
// grab the snake by the head
Coordinate head = mSnakeTrail.get(0);
Coordinate newHead = new Coordinate(1, 1);
mDirection = mNextDirection;
switch (mDirection) {
case EAST: {
newHead = new Coordinate(head.x + 1, head.y);
break;
}
case WEST: {
newHead = new Coordinate(head.x - 1, head.y);
break;
}
case NORTH: {
newHead = new Coordinate(head.x, head.y - 1);
break;
}
case SOUTH: {
newHead = new Coordinate(head.x, head.y + 1);
break;
}
}
// Collision detection
// For now we have a 1-square wall around the entire arena
if ((newHead.x < 1) || (newHead.y < 1) || (newHead.x > mXTileCount - 2)
|| (newHead.y > mYTileCount - 2)) {
MediaPlayer mpOver = activity.getMpOver();
mpOver.start();
setMode(LOSE);
return;
}
// Look for collisions with itself
int snakelength = mSnakeTrail.size();
for (int snakeindex = 0; snakeindex < snakelength; snakeindex++) {
Coordinate c = mSnakeTrail.get(snakeindex);
if (c.equals(newHead)) {
setMode(LOSE);
//mpOver.start();
return;
}
}
// Look for apples
int applecount = mAppleList.size();
for (int appleindex = 0; appleindex < applecount; appleindex++) {
Coordinate c = mAppleList.get(appleindex);
if (c.equals(newHead)) {
mAppleList.remove(c);
addRandomApple();
mScore++;
mMoveDelay *= 0.9;
growSnake = true;
}
}
// push a new head onto the ArrayList and pull off the tail
mSnakeTrail.add(0, newHead);
// except if we want the snake to grow
if (!growSnake) {
mSnakeTrail.remove(mSnakeTrail.size() - 1);
}
int index = 0;
for (Coordinate c : mSnakeTrail) {
if (index == 0) {
setTile(YELLOW_STAR, c.x, c.y);
} else {
setTile(RED_STAR, c.x, c.y);
}
index++;
}
}
/**
* Simple class containing two integer values and a comparison function.
* There's probably something I should use instead, but this was quick and
* easy to build.
*
*/
private class Coordinate {
public int x;
public int y;
public Coordinate(int newX, int newY) {
x = newX;
y = newY;
}
public boolean equals(Coordinate other) {
if (x == other.x && y == other.y) {
return true;
}
return false;
}
@Override
public String toString() {
return "Coordinate: [" + x + "," + y + "]";
}
}
}
Snake视图代码如下：
public class Snake extends Activity {
private SnakeView mSnakeView;
private static String ICICLE_KEY = "snake-view";
MediaPlayer mpOver;
public MediaPlayer getMpOver() {
return mpOver;
}
/**
* Called when Activity is first created. Turns off the title bar, sets up
* the content views, and fires up the SnakeView.
*
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.snake_layout);
mpOver.create(Snake.this, R.raw.bump);
mSnakeView = (SnakeView) findViewById(R.id.snake);
mSnakeView.setTextView((TextView) findViewById(R.id.text));
mSnakeView.setActivity(this);
if (savedInstanceState == null) {
// We were just launched -- set up a new game
mSnakeView.setMode(SnakeView.READY);
} else {
// We are being restored
Bundle map = savedInstanceState.getBundle(ICICLE_KEY);
if (map != null) {
mSnakeView.restoreState(map);
} else {
mSnakeView.setMode(SnakeView.PAUSE);
}
}
}
@Override
protected void onPause() {
super.onPause();
// Pause the game along with the activity
mSnakeView.setMode(SnakeView.PAUSE);
}
@Override
public void onSaveInstanceState(Bundle outState) {
//Store the game state
outState.putBundle(ICICLE_KEY, mSnakeView.saveState());
}
}
我们现在正在某个地方......它并没有崩溃，但也没有播放音频。这就是我在Android显示器中看到的内容。
02-15 10：18：13.409 17511-17511 /？我/艺术：不迟到-Xcheck：jni（已经开启） 02-15 10：18：13.478 17511-17511 / com.example.android.snake W / System：ClassLoader引用未知路径：/data/app/com.example.android.snake-1/lib/x86 02-15 10：18：13.486 17511-17511 / com.example.android.snake I / InstantRun：即时运行运行时启动。 Android包是com.example.android.snake，真正的应用程序类是null。 02-15 10：18：13.671 17511-17511 / com.example.android.snake W / System：ClassLoader引用未知路径：/data/app/com.example.android.snake-1/lib/x86 02-15 10：18：13.787 17511-17511 / com.example.android.snake D / MediaPlayer：MediaPlayer中的setSubtitleAnchor 02-15 10：18：18.037 17511-17511 / com.example.android.snake D / gralloc_ranchu：gralloc_unregister_buffer：退出HostConnection（是缓冲区处理线程） 02-15 10：18：28.095 17511-17511 / com.example.android.snake E / MediaPlayer：在状态1中调用 02-15 10：18：28.095 17511-17511 / com.example.android.snake E / MediaPlayer：错误（-38,0） 02-15 10：18：28.096 17511-17511 / com.example.android.snake E / MediaPlayer：错误（-38,0）
我添加了 activity.startMpOver（）; 它希望我将以下方法添加到Snake视图中。我添加了它，没有任何改变。所以我将mpOver.start（）添加到方法中。仍然没有去。
public void startMpOver() {
mpOver.start();
}
我还是得到了这个
02-15 11：11：56.049 23934-23934 / com.example.android.snake E / MediaPlayer：在状态1中调用 02-15 11：11：56.049 23934-23934 / com.example.android.snake E / MediaPlayer：错误（-38,0） 02-15 11：11：56.057 23934-23934 / com.example.android.snake E / MediaPlayer：错误（-38,0） 02-15 11：12：17.878 23934-23934 / com.example.android.snake E / MediaPlayer：在状态0中调用 02-15 11：12：43.165 23934-23934 / com.example.android.snake E / MediaPlayer：在状态0中调用 02-15 11：12：52.872 23934-23934 / com.example.android.snake E / MediaPlayer：在状态0中调用
答案 0 :(得分：0)
尝试将您的Snake活动类更改为：
public class Snake extends Activity {
private SnakeView mSnakeView;
private static String ICICLE_KEY = "snake-view";
MediaPlayer mpOver;
boolean mpOverPrepared = false;
public MediaPlayer getMpOver() {
return mpOver;
}
/**
* Called when Activity is first created. Turns off the title bar, sets up
* the content views, and fires up the SnakeView.
*
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.snake_layout);
mpOver = new MediaPlayer();
mpOver.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mediaPlayer) {
mpOverPrepared = true;
}
});
mpOver.create(Snake.this, R.raw.bump);
mSnakeView = (SnakeView) findViewById(R.id.snake);
mSnakeView.setTextView((TextView) findViewById(R.id.text));
mSnakeView.setActivity(this);
if (savedInstanceState == null) {
// We were just launched -- set up a new game
mSnakeView.setMode(SnakeView.READY);
} else {
// We are being restored
Bundle map = savedInstanceState.getBundle(ICICLE_KEY);
if (map != null) {
mSnakeView.restoreState(map);
} else {
mSnakeView.setMode(SnakeView.PAUSE);
}
}
}
@Override
protected void onPause() {
super.onPause();
// Pause the game along with the activity
mSnakeView.setMode(SnakeView.PAUSE);
}
@Override
public void onSaveInstanceState(Bundle outState) {
//Store the game state
outState.putBundle(ICICLE_KEY, mSnakeView.saveState());
}
public void startMpOver() {
if(mpOverPrepared) {
mpOver.start();
}
}
}
然后，当你想在SnakeView中播放mpOver时，你可以这样做
activity.startMpOver();