我有关于空指针异常的错误，我无法在程序中找到错误的确切位置。我在网上搜索了可能的解决方案，但我发现它们都没有用。我知道Null Pointer Exception是什么，但是我无法确定我的代码中出了什么问题。任何帮助将不胜感激，谢谢。
这是我的代码：
LevelOneScreen.java
public class LevelOneScreen implements Screen {
private final ThumbChase app;
WalkAnimate walkAnimate;
private Stage stage;
private Image levelOneImage;
private Image holdStartImage;
public Image walkRightImage;
public Image walkLeftImage;
public float deltaTime = Gdx.graphics.getDeltaTime();
public LevelOneScreen(final ThumbChase app){
this.app = app;
this.stage = new Stage(new StretchViewport(app.screenWidth,app.screenHeight , app.camera));
}
@Override
public void show() {
Gdx.input.setInputProcessor(stage);
walkAnimate = new WalkAnimate();
levelOneBackground();
holdStart();
ninjaWalk(); ==>ERROR1:LevelOneScreen.java:54
}
public void holdStart(){
Texture holdStartTexture = new Texture("HoldStart.png");
holdStartImage = new Image(holdStartTexture);
float holdStartImageW = holdStartImage.getWidth();
float holdStartImageH = holdStartImage.getHeight();
float holdStartImgWidth = app.screenWidth*0.8f;
float holdStartImgHeight = holdStartImgWidth *(holdStartImageH/holdStartImageW);
holdStartImage.isTouchable();
holdStartImage.setSize(holdStartImgWidth,holdStartImgHeight);
holdStartImage.setPosition(stage.getWidth()/2-holdStartImgWidth/2,stage.getHeight()/2-holdStartImgHeight/2);
stage.addActor(holdStartImage);
holdStartImage.addListener(new ActorGestureListener(){
public void touchDown (InputEvent event, float x, float y, int pointer, int button){
holdStartImage.setVisible(false);
};
});
}
public void levelOneBackground(){
Texture levelOneTexture = new Texture("BGBlue Resize.png");
levelOneImage = new Image(levelOneTexture);
levelOneImage.setSize(app.screenWidth,app.screenHeight);
levelOneImage.setPosition(0,0);
stage.addActor(levelOneImage);
levelOneImage.addListener(new ActorGestureListener(){
public void touchDown (InputEvent event, float x, float y, int pointer, int button){
holdStartImage.setVisible(false);
};
});
}
public void ninjaWalk(){
ERROR2==> TextureRegion ninjaWalkRight = new TextureRegion(walkAnimate.getCurrentFrameRight());
TextureRegion ninjaWalkLeft = new TextureRegion(walkAnimate.getCurrentFrameLeft());
walkRightImage = new Image(ninjaWalkRight);
walkLeftImage = new Image(ninjaWalkLeft);
float walkImageW = walkRightImage.getWidth();
float walkImageH = walkRightImage.getHeight();
float walkImageWidth = app.screenWidth*0.15f;
float walkImageHeight = walkImageWidth*(walkImageH/walkImageW);
walkLeftImage.isTouchable();
walkRightImage.isTouchable();
walkRightImage.setSize(walkImageWidth,walkImageHeight);
walkLeftImage.setSize(walkImageWidth,walkImageHeight);
walkRightImage.setPosition(stage.getWidth()/2-walkImageWidth/2,0);
walkLeftImage.setPosition(stage.getWidth()/2-walkImageWidth/2,0);
walkLeftImage.addAction(moveBy(3f,3f,3f));
stage.addActor(walkLeftImage);
}
@Override
public void render(float delta) {
Gdx.gl.glClearColor(0, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
walkAnimate.update(deltaTime);
update(delta);
}
public void update(float delta){
stage.act(delta);
stage.draw();
app.batch.begin();
app.batch.end();
}
@Override
public void resize(int width, int height) {
}
@Override
public void pause() {
}
@Override
public void resume() {
}
@Override
public void hide() {
}
@Override
public void dispose() {
stage.dispose();
}
}
WalkAnimate.java
public class WalkAnimate {
public ThumbChase app;
public Stage stage;
private Animation walkAnimationRight;
private Animation walkAnimationLeft;
private Texture walkSheetRight;
private Texture walkSheetLeft;
private TextureRegion[] walkFramesRight;
private TextureRegion[] walkFramesLeft;
private TextureRegion currentFrameRight;
private TextureRegion currentFrameLeft;
private float stateTime;
private Rectangle bound; //used for positioning and collision detection
private static final int FRAME_COLS_WALK = 3;
private static final int FRAME_ROWS_WALK= 2;
private float screenWidth = Gdx.graphics.getWidth();
private float screenHeight = Gdx.graphics.getHeight();
public float currentFrameWidth = (float)(screenHeight*0.15);
public float currentFrameHeight = (float)(screenHeight*0.15);
public float walkSheetWidth;
public float walkSheetHeight;
public WalkAnimate () {
walkSheetRight = new Texture("ninjaWalkRight.png");
walkSheetWidth = walkSheetRight.getWidth();
walkSheetHeight = walkSheetRight.getWidth();
TextureRegion[][] tmp = TextureRegion.split(walkSheetRight, (int) walkSheetRight.getWidth() / FRAME_COLS_WALK, (int) walkSheetRight.getHeight() / FRAME_ROWS_WALK);
walkFramesRight = new TextureRegion[FRAME_COLS_WALK * FRAME_ROWS_WALK];
int index = 0 ;
for (int i = 0; i < FRAME_ROWS_WALK; i++) {
for (int j = 0; j < FRAME_COLS_WALK; j++) {
walkFramesRight[index++] = tmp[i][j];
}
}
walkAnimationRight = new Animation(0.044f, walkFramesRight);
stateTime = 0f;
walkSheetLeft = new Texture("ninjaWalkLeft.png");
walkSheetWidth = walkSheetLeft.getWidth();
walkSheetHeight = walkSheetLeft.getWidth();
TextureRegion[][] tmp1 = TextureRegion.split(walkSheetLeft, (int) walkSheetRight.getWidth() / FRAME_COLS_WALK, (int)walkSheetLeft.getHeight() / FRAME_ROWS_WALK);
walkFramesLeft = new TextureRegion[FRAME_COLS_WALK * FRAME_ROWS_WALK];
int index1 = 0;
for (int i = 0; i < FRAME_ROWS_WALK; i++) {
for (int j = 0; j < FRAME_COLS_WALK; j++) {
walkFramesLeft[index1++] = tmp1 [i][j];
}
}
walkAnimationLeft = new Animation(0.044f, walkFramesLeft);
stateTime = 0f;
}
public Rectangle getBound(){
return bound;
}
public void update(float delta){
stateTime += delta;
currentFrameRight = walkAnimationRight.getKeyFrame(stateTime, true);
currentFrameLeft = walkAnimationLeft.getKeyFrame(stateTime, true);
}
public TextureRegion getCurrentFrameRight(){
return currentFrameRight;
}
public TextureRegion getCurrentFrameLeft(){
return currentFrameLeft;
}
}
这就是错误：
> java.lang.NullPointerException
> at
> com.badlogic.gdx.graphics.g2d.TextureRegion.setRegion(TextureRegion.java:112)
> at
> com.badlogic.gdx.graphics.g2d.TextureRegion.<init>(TextureRegion.java:63)
> at
> com.jpfalmazan.thumbchaseninja.GameScreens.LevelOneScreen.show(LevelOneScreen.java:54)
> at com.badlogic.gdx.Game.setScreen(Game.java:61)
> at
> com.jpfalmazan.thumbchaseninja.GameScreens.MenuScreen$1.clicked(MenuScreen.java:82)
> at
> com.badlogic.gdx.scenes.scene2d.utils.ClickListener.touchUp(ClickListener.java:89)
> at
> com.badlogic.gdx.scenes.scene2d.InputListener.handle(InputListener.java:58)
> at com.badlogic.gdx.scenes.scene2d.Stage.touchUp(Stage.java:353)
> at
> com.badlogic.gdx.backends.android.AndroidInput.processEvents(AndroidInput.java:379)
> at
> com.badlogic.gdx.backends.android.AndroidGraphics.onDrawFrame(AndroidGraphics.java:457)
> at
> android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1516)
> at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)
答案 0 :(得分：0)
你可以在logcat日志中找到确切的行，你可以看到活动名称和代码行，点击它就可以重定向到同一行的各个Activity ..
希望这会对你有所帮助。
答案 1 :(得分：0)
在第一次致电walkAnimate.update(dt)之前，您似乎没有致电walkAnimate.getCurrentFrameRight()，因此walkAnimate.getCurrentFrameRight()会返回null。
此外，在ninjaWalk()中您创建了两个actor（walkRightImage和walkLeftImage），只向舞台添加一个并且永远不会更新它的纹理。你应该重新设计你的概念：在启动时创建一个actor，将它存储在一个字段中，并在渲染/更新方法中更改它的纹理。
答案 2 :(得分：0)
您的一个纹理要么命名错误，要么在加载之前尝试访问它。
你可以告诉这个例外;
com.badlogic.gdx.graphics.g2d.TextureRegion.setRegion(TextureRegion.java:112)
这意味着纹理区域无法将纹理标识符映射到程序中的有效纹理，因此ninjaWalkRight或ninjaWalkLeft不存在或未加载。
如果您使用纹理打包器，请确保您的文件名为ninjaWalkRight和ninjaWalkLeft。
同样使用AssetManager确保在尝试访问这些文件之前加载这些文件，因为这也可能是一个问题。