我希望我的物体撞墙。当我的精灵碰撞时，我想发布一个新的屏幕，上面写着“你崩溃了”。
我不断收到同样的错误！
package com.example.rushhour;
import java.util.Random;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.media.MediaPlayer;
public class TrafficSprite extends PlayScreen {
Random rand = new Random();
private int x = 5;
private int y = 30;
private int xSpeed = 0;
private int ySpeed = 0;
private GameView gameView;
private PlayScreen playScreen;
private Sprite sprite;
private Bitmap bmp;
private int width;
private int height;
private MediaPlayer crashsound;
public TrafficSprite(GameView gameView, Bitmap bmp) {
this.gameView = gameView;
this.playScreen = playScreen;
this.sprite = sprite;
this.bmp = bmp;
this.width = bmp.getWidth();
this.height = bmp.getHeight();
System.out.println(gameView.getWidth());
int randomwidth = gameView.getWidth();
Math.abs(randomwidth);
x=rand.nextInt(760);
}
private void update(){
collision();
ySpeed = 10;
y+=ySpeed;
}
**private void collision(){
Rect policerect = new Rect(Sprite.getPolicex(),Sprite.getPolicey(),Sprite.getPolicex()+Sprite.getPoliceWidth(),Sprite.getPolicey()+Sprite.getPoliceHeight());
Rect trafficsprite = new Rect(x,y,x+bmp.getWidth(),y+bmp.getHeight());
if (Rect.intersects(policerect, trafficsprite)){
GameView.getCrashSound().start();
CrashScreen();
}
}
public void CrashScreen(){
System.out.println("hi");
Intent intent = new Intent(this, Crash.class);
startActivity(intent);
}**
public void drawTraffic(Canvas canvas) {
update();
Rect src = new Rect (0,0,width,height);
Rect dst = new Rect (x,y,x+width,y+height);
canvas.drawBitmap(bmp, src, dst, null);
}
}
这是我创建意图的地方：
public void CrashScreen(){
System.out.println("hi");
Intent intent = new Intent(this, Crash.class);
startActivity(intent);
这是错误：
FATAL EXCEPTION: Thread-6714
12-03 17:57:46.497: E/AndroidRuntime(6013): Process: com.example.rushhour, PID: 6013
12-03 17:57:46.497: E/AndroidRuntime(6013): java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
12-03 17:57:46.497: E/AndroidRuntime(6013): at android.content.ContextWrapper.getPackageName(ContextWrapper.java:131)
12-03 17:57:46.497: E/AndroidRuntime(6013): at android.content.ComponentName.<init>(ComponentName.java:77)
12-03 17:57:46.497: E/AndroidRuntime(6013): at android.content.Intent.<init>(Intent.java:3996)
12-03 17:57:46.497: E/AndroidRuntime(6013): at com.example.rushhour.TrafficSprite.CrashScreen(TrafficSprite.java:65)
12-03 17:57:46.497: E/AndroidRuntime(6013): at com.example.rushhour.TrafficSprite.collision(TrafficSprite.java:58)
12-03 17:57:46.497: E/AndroidRuntime(6013): at com.example.rushhour.TrafficSprite.update(TrafficSprite.java:45)
12-03 17:57:46.497: E/AndroidRuntime(6013): at com.example.rushhour.TrafficSprite.drawTraffic(TrafficSprite.java:82)
12-03 17:57:46.497: E/AndroidRuntime(6013): at com.example.rushhour.GameView.createTraffic(GameView.java:218)
12-03 17:57:46.497: E/AndroidRuntime(6013): at com.example.rushhour.GameLoopThread.run(GameLoopThread.java:25)
Play Screen是Activity，它顶部有一个“gameView”
setContentView(new GameView(this));
Gameview：
package com.example.rushhour;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import android.content.Context;
import android.content.Intent;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.media.MediaPlayer;
import android.os.Handler;
import android.os.Looper;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
public class GameView extends SurfaceView {
private Bitmap background,police,audi;
private Sprite policesprite;
private TrafficSprite audisprite;
private List<TrafficSprite> trafficsprites = new ArrayList<TrafficSprite>();
private SurfaceHolder holder;
private GameLoopThread gameLoopThread;
private int x = 0;
final Handler handler = new Handler();
private int i =-1;
public static MediaPlayer crashsound;
public GameView(Context context) {
super(context);
gameLoopThread = new GameLoopThread(this);
holder = getHolder();
crashsound = MediaPlayer.create(context, R.raw.crash);
holder.addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
boolean retry = true;
gameLoopThread.setRunning(false);
while (retry){
try {
gameLoopThread.join();
retry = false;
} catch (InterruptedException e) {
}
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
createSprites();
gameLoopThread.setRunning(true);
gameLoopThread.start();
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format,
int width, int height) {
}
});
background = BitmapFactory.decodeResource(getResources(), R.drawable.playbackground);
police = BitmapFactory.decodeResource(getResources(), R.drawable.policered);
audi = BitmapFactory.decodeResource(getResources(), R.drawable.audi);
policesprite = new Sprite(this,police);
audisprite = new TrafficSprite(this,audi);
}
private void createSprites() {
final int[] spriteID = {
R.drawable.amb,
R.drawable.audi,
R.drawable.car,
R.drawable.mini,
R.drawable.truck,
R.drawable.taxi,
R.drawable.van
// etc for as many images you have
};
new Thread(new Runnable() {
public void run() {
Looper.prepare();
for(int i = 0; i < 6; i++) {
if (i == 5){
mediumspeed();
}
Random generator = new Random();
int randomImageId = spriteID[generator.nextInt(spriteID.length)];
trafficsprites.add(createSprite(randomImageId));
try
{
Thread.sleep(3000); //Waits for 1 second
}
catch(InterruptedException e)
{
e.printStackTrace();
}
}
}
}).start();
}
public void mediumspeed(){
final int[] spriteID = {
R.drawable.amb,
R.drawable.audi,
R.drawable.car,
R.drawable.mini,
R.drawable.truck,
R.drawable.taxi,
R.drawable.van
// etc for as many images you have
};
new Thread(new Runnable() {
public void run() {
Looper.prepare();
for(int i = 0; i < 6; i++) {
if (i==5){
fastspeed();
}
Random generator = new Random();
int randomImageId = spriteID[generator.nextInt(spriteID.length)];
trafficsprites.add(createSprite(randomImageId));
try
{
Thread.sleep(1850); //Waits for 1 second
}
catch(InterruptedException e)
{
e.printStackTrace();
}
}
}
}).start();
}
public void fastspeed(){
final int[] spriteID = {
R.drawable.amb,
R.drawable.audi,
R.drawable.car,
R.drawable.mini,
R.drawable.truck,
R.drawable.taxi,
R.drawable.van
// etc for as many images you have
};
new Thread(new Runnable() {
public void run() {
Looper.prepare();
for(int i = 0; i < 6; i++) {
Random generator = new Random();
int randomImageId = spriteID[generator.nextInt(spriteID.length)];
trafficsprites.add(createSprite(randomImageId));
try
{
Thread.sleep(1200); //Waits for 1 second
}
catch(InterruptedException e)
{
e.printStackTrace();
}
}
}
}).start();
}
private TrafficSprite createSprite(int resouce) {
Bitmap bmp = BitmapFactory.decodeResource(getResources(), resouce);
return new TrafficSprite(this,bmp);
}
@Override
protected void onDraw(Canvas canvas){
canvas.drawBitmap(background, 0, 0, null);
policesprite.onDraw(canvas);
}
protected void createTraffic(Canvas canvas){
for (TrafficSprite trafficsprite : trafficsprites) {
trafficsprite.drawTraffic(canvas);
}
}
protected void createTraffic1(Canvas canvas){
trafficsprites.get(1).drawTraffic(canvas);
}
public static MediaPlayer getCrashSound(){
return crashsound;
}
当精灵碰撞时，我希望它打开一个新的活动，主精灵位于屏幕的底部，并有自己的类Sprite.java，其他每个精灵都由TrafficSprite.java控制
答案 0 :(得分：0)
试试这段代码：
public void CrashScreen(){
Intent intent = new Intent(this, Crash.class);
startActivity(intent);
}
并在新的Activity中设置一个带有要显示的文本的TextView。
答案 1 :(得分：0)
也许您需要当前活动的conext，通常是MainActivity：
public void CrashScreen(){
Intent intent = new Intent(getActivity().getApplicationContext(), Crash.class);
startActivity(intent);
}
考虑到您使用的是明确的意图，因此您需要运行确切的类，并使用上下文作为documentation says
进行解析答案 2 :(得分：0)
根据堆栈跟踪，您的错误发生here。问题是mBase是null，这意味着您的上下文未初始化。这可能由于各种原因而发生
请检查以下内容：
是清单中列出的这种活动吗？
Activty的onCreate方法是否正确完成？
这个方法是在onCreate之后调用的吗？
我确信上述问题之一就是问题。
修改
要解决您的问题：
：
PlayScreennew TrafficSprite(this,.....) //refers to the activty
中的：
TrafficSprite通过这样做，您将拥有有效的上下文。
您的解决方案的问题是，虽然您创建了一个 private Context cntx;
public TrafficSprite(Context context,GameView gameView, Bitmap bmp)
{
cntx=context;
....
public void CrashScreen(){
System.out.println("hi");
Intent intent = new Intent(cntx, Crash.class);
startActivity(intent);
}
的类TrafficSprite，但它的上下文创建方法根本没有被调用（例如Activity没有叫）。
<强> EDIT2：
SurfaceView类中已有一个getContext()方法，因此可以使用。
onCreate由于您的SurfaceView具有activty的上下文，因此这也应该很好。