[英]Application crashes upon touching screen
So I am making a simple treasure hunter game.所以我正在制作一个简单的寻宝游戏。 I have implemented the SurfaceHolder.Callback and OnTouchListener methods.
我已经实现了 SurfaceHolder.Callback 和 OnTouchListener 方法。 When touching the screen to dig for the treasure the app crashes.
当触摸屏幕挖掘宝藏时,应用程序崩溃。
Here is the code for the DrawSurface class:这是 DrawSurface class 的代码:
public class DrawSurface extends SurfaceView implements SurfaceHolder.Callback, View.OnTouchListener {
private static ArrayList<Item> mInventory;
private final Rect mFieldDim = new Rect();
private ArrayList<Item> mItems;
private ArrayList<PointF> dugHoles;
private Bitmap mBMPField;
private Bitmap mBMPHole;
private SurfaceHolder mHolder;
private MotionEvent motionEvent;
public DrawSurface(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public static ArrayList<Item> getInventory() {
return mInventory;
}
public void init() {
getHolder().addCallback(this);
setOnTouchListener(this);
mItems = loadItems();
dugHoles = new ArrayList<PointF>();
mBMPField = BitmapFactory.decodeResource(getResources(), R.drawable.field);
mBMPHole = BitmapFactory.decodeResource(getResources(), R.drawable.hole);
mInventory = new ArrayList<Item>();
}
public void surfaceCreated(SurfaceHolder surfaceHolder) {
mHolder = surfaceHolder;
Canvas c = mHolder.lockCanvas();
mFieldDim.set(0, 0, c.getWidth(), c.getHeight());
mHolder.unlockCanvasAndPost(c);
for (int i = 0; i < mItems.size(); i++) {
mItems.get(i).x = (int) (Math.random() * (float) mFieldDim.width());
mItems.get(i).y = (int) (Math.random() * (float) mFieldDim.height());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int i, int i2, int i3) {
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
public boolean onTouch(View v, MotionEvent event) {
if (!(motionEvent.getAction() != MotionEvent.ACTION_DOWN)) {
PointF touch = new PointF(motionEvent.getX(), motionEvent.getY());
dugHoles.add(touch);
int radius = Math.max(mBMPHole.getHeight(), mBMPHole.getWidth()) / 2;
for (int i = mItems.size() - 1; i >= 0; i--) {
Item item = mItems.get(i);
int dx = item.x - (int) touch.x;
int dy = item.y - (int) touch.y;
if (dx * dx + dy * dy < radius * radius) {
mItems.remove(i);
mInventory.add(item);
Toast toast = Toast.makeText(this.getContext(), item.name + "found", Toast.LENGTH_SHORT);
toast.show();
}
}
invalidate();
}
return true;
}
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mBMPField != null) {
canvas.drawBitmap(mBMPField, new Rect(0, 0, mBMPField.getWidth(), mBMPField.getHeight()), mFieldDim, new Paint());
}
if (mBMPHole != null) {
for (PointF hole : dugHoles) {
canvas.drawBitmap(mBMPHole,
new Rect(0, 0, mBMPHole.getWidth(), mBMPHole.getHeight()),
new RectF(hole.x - mBMPHole.getWidth() / 2, hole.y - mBMPHole.getHeight() / 2, hole.x + mBMPHole.getWidth() / 2, hole.y + mBMPHole.getHeight() / 2),
new Paint());
}
}
}
private ArrayList<Item> loadItems() {
InputStream input = getResources().openRawResource(R.raw.items);
BufferedReader reader = null;
ArrayList<Item> items = new ArrayList<Item>();
String itemName;
try {
reader = new BufferedReader(new InputStreamReader(input));
while ((itemName = reader.readLine()) != null) {
items.add(new Item(itemName));
}
} catch (Exception e) {
Log.e("MainActivity", "Reading list of items failed!", e);
} finally {
try {
if (reader != null) reader.close();
} catch (Exception e) {
Log.e("MainActivity", "Error closing file reader.", e);
}
}
return items;
}
Here is the error messages I recieve:这是我收到的错误消息:
E/AndroidRuntime: FATAL EXCEPTION: main Process: justinrhinehart.cse.fullsail.treasurehunter, PID: 23942 java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.MotionEvent.getAction()' on a null object reference at justinrhinehart.cse.fullsail.treasurehunter.DrawSurface.onTouch(DrawSurface.java:77) at android.view.View.dispatchTouchEvent(View.java:14305) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at ZC31B32364CE19CA8FC E/AndroidRuntime: FATAL EXCEPTION: main Process: justinrhinehart.cse.fullsail.treasurehunter, PID: 23942 java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.MotionEvent.getAction()' on a null object reference at justinrhinehart.cse.fullsail.treasurehunter.DrawSurface.onTouch(DrawSurface.java:77) at android.view.View.dispatchTouchEvent(View.java:14305) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android .view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at ZC31B32364CE19CA8FC D150A417ECCE58Z.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:
D150A417ECCE58Z.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup .dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup. java:2742) 在 android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java: 3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:488) at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1871) at android.app.Activity.dispatchTouchEvent(Activity.java:4125) at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69) at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:446) at android.view.View.dispatchPointerEvent(View.Z93F725A07423FE1C889F448B33D2
3118) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2742) at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:488) at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow .java:1871) at android.app.Activity.dispatchTouchEvent(Activity.java:4125) at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69) at com.android.internal.policy.DecorView.dispatchTouchEvent( DecorView.java:446) 在 android.view.View.dispatchPointerEvent(View.Z93F725A07423FE1C889F448B33D2 1F46Z:14568) at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6016) at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5819) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5310) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5367) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5333) at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:5485) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5341) at android
1F46Z:14568) at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6016) at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5819) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl .java:5310) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5367) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5333) at android.view.ViewRootImpl$AsyncInputStage.forward( ViewRootImpl.java:5485) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5341) at android .view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5542) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5314) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5367) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5333) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5341) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5314) at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8080) at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8
.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5542) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5314) at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5367) at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5333) at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5341) at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5314) at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8080) at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8 031) at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:7992) at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8203) at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:220) at android.os.MessageQueue.nativePollOnce(Native Method) at android.os.MessageQueue.next(MessageQueue.java:335) at android.os.Looper.loop(Looper.java:183) at android.app.ActivityThread.main(ActivityThread.java:7656) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.
031) at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:7992) at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8203) at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:220) at android.os.MessageQueue.nativePollOnce(Native Method) at android.os.MessageQueue.next(MessageQueue.java:335) at android.os.Looper.loop(Looper.java:183) at android.app.ActivityThread.main( ActivityThread.java:7656) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os. RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Can anyone help me understand what the problem is?谁能帮我理解问题是什么?
You're trying to use a variable with an unassigned value when I think you meant to use the event
parameter of your onTouch()
.当我认为您打算使用
onTouch()
的event
参数时,您正在尝试使用具有未分配值的变量。 You should edit your onTouch to look something like this:你应该编辑你的 onTouch 看起来像这样:
public boolean onTouch(View v, MotionEvent event) {
if (!(event.getAction() != MotionEvent.ACTION_DOWN)) {
PointF touch = new PointF(event.getX(), event.getY());
// ...
}
}
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