Android开发：“线程退出且未捕获异常”

编程问答 2022-04-26

问题描述

| 我正在尝试创建我的第一个Android应用程序（游戏），但是上手时遇到了一些困难。 当我运行代码时，出现以下错误日志： 
05-25 02:41:51.022: WARN/dalvikvm(634): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
05-25 02:41:51.040: ERROR/AndroidRuntime(634): FATAL EXCEPTION: main
05-25 02:41:51.040: ERROR/AndroidRuntime(634): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.stickfigs.nmg/com.stickfigs.nmg.NMG}: java.lang.NullPointerException
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2663)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.os.Looper.loop(Looper.java:123)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.main(ActivityThread.java:4627)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at java.lang.reflect.Method.invokeNative(Native Method)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at java.lang.reflect.Method.invoke(Method.java:521)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at dalvik.system.NativeStart.main(Native Method)
05-25 02:41:51.040: ERROR/AndroidRuntime(634): Caused by: java.lang.NullPointerException
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at com.stickfigs.nmg.NMG.onCreate(NMG.java:32)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2627)
05-25 02:41:51.040: ERROR/AndroidRuntime(634):     ... 11 more
05-25 02:41:51.062: WARN/ActivityManager(59):   Force finishing activity com.stickfigs.nmg/.NMG
我认为问题出在“线程退出并带有未捕获的异常”部分，我不知道异常可能是什么或导致异常的原因。 这是我的代码： NMGView.java：     包com.stickfigs.NMG; 
import android.content.Context;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

class NMGView extends SurfaceView implements SurfaceHolder.Callback {

    class NMGThread extends Thread {
        //State-tracking constants
        public static final int STATE_LOSE = 1;
        public static final int STATE_PAUSE = 2;
        public static final int STATE_READY = 3;
        public static final int STATE_RUNNING = 4;
        public static final int STATE_WIN = 5;

        /** The state of the game. One of READY,RUNNING,PAUSE,LOSE,or WIN */
        private int mode;

        /** Handle to the surface manager object we interact with */
        private SurfaceHolder surfaceHolder;

        public NMGThread(SurfaceHolder surfaceHolderc,Context contextc) {
            // get handles to some important objects
            surfaceHolder = surfaceHolderc;
            context = contextc;

        }

        /**
         * Restores game state from the indicated Bundle. Typically called when
         * the Activity is being restored after having been prevIoUsly
         * destroyed.
         * 
         * @param savedState Bundle containing the game state
         */
        public synchronized void restoreState(Bundle savedState) {
            synchronized (surfaceHolder) {
                setState(STATE_PAUSE);
                }
        }

        /**
         * Sets the game mode. That is,whether we are running,paused,in the
         * failure state,in the victory state,etc.
         * 
         * @param mode one of the STATE_* constants
         * @param message string to add to screen or null
         */
        public void setState(int modec) {
            synchronized (surfaceHolder) {
                mode = modec;
            }
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder,int format,int width,int height) {
        // Todo Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // Todo Auto-generated method stub

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // Todo Auto-generated method stub

    }

    /** Handle to the application context,used to e.g. fetch Drawables. */
    private Context context;

    /** The thread that actually draws the animation */
    private NMGThread thread;

    public NMGView(Context context,AttributeSet attrs) {
        super(context,attrs);

        // register our interest in hearing about changes to our surface
        SurfaceHolder holder = getHolder();
        holder.addCallback(this);

        // create thread only; it\'s started in surfaceCreated()
        thread = new NMGThread(holder,context);

        setFocusable(true); // make sure we get key events
    }

    /**
     * Fetches the animation thread corresponding to this LunarView.
     * 
     * @return the animation thread
     */
    public NMGThread getThread() {
        return thread;
    }
}
NMG.java： 
package com.stickfigs.nmg;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Window;

import com.stickfigs.nmg.NMGView.NMGThread;

public class NMG extends Activity {
    /** Called when the activity is first created. */

    /** A handle to the thread that\'s actually running the animation. */
    private NMGThread nMGThread;

    /** A handle to the View in which the game is running. */
    private NMGView nMGView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //Turn off the window\'s title bar
        // Todo Turn off the status bar
        requestwindowFeature(Window.FEATURE_NO_TITLE);

        // tell system to use the layout defined in our XML file
        setContentView(R.layout.nmg_layout);

        // get handles to the LunarView from XML,and its LunarThread
        nMGView = (NMGView) findViewById(R.id.nmg);
        nMGThread = nMGView.getThread();

        if (savedInstanceState == null) {
            // we were just launched: set up a new game
            nMGThread.setState(NMGThread.STATE_READY);
            Log.w(this.getClass().getName(),\"SIS is null\");
        } else {
            // we are being restored: resume a prevIoUs game
            nMGThread.restoreState(savedInstanceState);
            Log.w(this.getClass().getName(),\"SIS is nonnull\");
        }
    }
}
更新：这是我的R.java和nmg_layout.xml： R.java：     包com.stickfigs.nmg; 
public final class R {
    public static final class attr {
    }
    public static final class drawable {
        public static final int icon=0x7f020000;
    }
    public static final class id {
        public static final int nmg=0x7f050000;
    }
    public static final class layout {
        public static final int nmg_layout=0x7f030000;
    }
    public static final class string {
        public static final int app_name=0x7f040001;
        public static final int hello=0x7f040000;
    }
}
nmg_layout.xml： 
<?xml version=\"1.0\" encoding=\"utf-8\"?>
<FrameLayout xmlns:android=\"http://schemas.android.com/apk/res/android\"
    android:layout_width=\"fill_parent\"
    android:layout_height=\"fill_parent\">

    <com.stickfigs.nmg.NMGView
      android:id=\"@+id/nmg\"
      android:layout_width=\"fill_parent\"
      android:layout_height=\"fill_parent\"/>
</FrameLayout>
    

解决方法

如果查看堆栈跟踪，将看到\“ Caused by ... \”行（有时不止一个）。其中的最后一个是重要的。它说NMG.java的第32行有一个空指针异常。该行及其前面的行是： 
nMGView = (NMGView) findViewById(R.id.nmg);
nMGThread = nMGView.getThread();
显然，布局
R.layout.nmg_layout
中没有ID为
R.id.nmg
的视图。这就是导致您出现问题的原因。     ,在您的XML文件中，确实存在
R.id.nmg
。 因此，我认为问题是由资源中的“ 9”对象膨胀引起的。 您应该检查
NMGView
源代码，尤其是在其构造函数中。     ,如果您在\“ build.gradle（Module：app）\”中使用\“ multiDexEnabled true \”，请从\“ defaultConfig \”中删除此行并同步项目。 在我的情况下有效！！！     ,发生此问题的原因是，在大多数情况下，销毁surfaceView时，SurfaceView onDraw（）方法正在运行，然后会出现NULL POINTER ERROR，这是因为画布当时不存在。我已经解决了使用NullPointerException捕获所有绘图内容的问题： 
@Override
public void onDraw(Canvas canvas) {

    try {
         //Drawing Stuff

   }catch(NullPointerException e){
        Log.e(\"NULL POINTER EXCEPTION\",\"Canvas NULL POINTER\");
    }
}
如果在Main活动中实现onPause（）和onDestroy（）方法，则将获得以下顺序：首先：E / onPause：暂停->下一个E / surfaceDestroyed：表面破坏-> E / NULL POINTER EXCEPTION：画布NULL POINTER->最终 E / onDestroy：毁灭 这是我正在使用的surfaceDestroyed方法： 
   @Override
public void surfaceDestroyed(SurfaceHolder arg0) {
    Log.e(\"surfaceDestroyed\",\"SURFACE DESTROYED \");


    thread.setRunning(false);
        try {
            //thread.setRunning(false);
            thread.join();
            } catch (InterruptedException e) {
           Log.e(\"Surface Thread Stopped\",\"SURFACE THREAD STOPPED\");
        }

}
    
androidandroid开发开发开发异常异常异常捕获捕获线程线程退出退出