Onclick，java.lang.IllegalStateException的错误：无法执行活动的方法

Question

每当我点击撤消并重做时，我都有错误，我不知道为什么我有这个错误

java.lang.IllegalStateException: Could not execute method of the activity. 

任何人都可以请帮助我这个。 在此先感谢。 下面是我的代码和错误日志

--Draw类

public class Draw extends Activity implements { 

public static String filex; 

private static final int SELECT_PICTURE = 1; 

public static String selectedImagePath; 
public static Bitmap cBitmap; 

public static Integer resize; 
public static Integer imageBackgroundEraser; 
// Instance variables 

public static Paint  mPaint; 
private MaskFilter mEmboss; 
private MaskFilter mBlur; 
private MyView  mView; 
private int mImageCount = 0; 
private int mLastBg = 0; 

public static Integer WW; 
public static Integer WH; 

private float BrushWidth; 
private int thickness; 
private int BrushColor; 
public static int backgroundColor; 
float Mx1,My1; 
float x,y; 

@SuppressWarnings("deprecation") 
@Override 

public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_draw); 

    Display display = getWindowManager().getDefaultDisplay(); //*** 


    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_draw4_fun_main); 

    Display display = getWindowManager().getDefaultDisplay(); //*** 

    WH = display.getHeight(); //*** 
    WW = display.getWidth(); //*** 

    final MyView myView = new MyView(this); 
    frm_layout=(FrameLayout) findViewById(R.id.main_frame); 
    frm_layout.addView(myView); 


    setInitialPaint(); 
    backgroundColor = Color.WHITE; 

} 

private void setInitialPaint() { 
    //bgColor = 0xFFFFFFFF; // default bg color white 
    BrushWidth = 3; 
    BrushColor = 0xFF000000; //** 
    mPaint = new Paint(); 
    mPaint.setAntiAlias(true); 
    mPaint.setDither(true); 
    mPaint.setColor(BrushColor); 
    mPaint.setStyle(Paint.Style.STROKE); 
    mPaint.setStrokeJoin(Paint.Join.ROUND); 
    mPaint.setStrokeCap(Paint.Cap.ROUND); 
    mPaint.setStrokeWidth(BrushWidth); 
    mPaint.setPathEffect(new CornerPathEffect(30)); 
    //mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 },0.4f, 6, 3.5f); 

    //mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL); 
} 

public void onClick(View view){ 
    switch (view.getId()){ 
    case R.id.undoBtn: 
     mView.onClickUndo(); 
    break; 

    case R.id.redoBtn: 
     mView.onClickRedo(); 
    break; 

    case R.id.saveBtn: 
     File myDir=new File("/sdcard/Pictures/Draw"); 
     myDir.mkdirs(); 
     String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date(System.currentTimeMillis())); //*** 
     String fname = timeStamp + ".png"; 
     File file = new File (myDir, fname); 
     System.out.println(file+"----> file"); 
     if (file.exists()) file.delete(); 
     saveAsPng(file); 
    break; 


    } 
} 

public void saveAsPng (File f) 
{ 
    String fname = f.getAbsolutePath(); 

    FileOutputStream fos = null; 
    try { 
     fos = new FileOutputStream (f); 
     mView.mBitmap.compress (CompressFormat.PNG, 100, fos); 
     sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://"+ Environment.getExternalStorageDirectory()))); 
     Toast.makeText (getApplicationContext(), "Saved " + fname, Toast.LENGTH_LONG).show(); 
    } catch (Throwable ex) { 
     Toast.makeText (getApplicationContext(), "Error: " + ex.getMessage(), Toast.LENGTH_LONG).show(); 
     ex.printStackTrace(); 
    } 

} // end saveAsPng 

} // end Main 

--- MyView的类

public class MyView extends View { 

/** 
*/ 
// Constants and variables 
    private static final float MINP = 0.25f; 
    private static final float MAXP = 0.75f; 

    public static Bitmap mBitmap; 
    private Canvas mCanvas; 
    private Path mPath; 
    private Paint mBitmapPaint; 
    private ArrayList<Path> paths = new ArrayList<Path>(); 
    private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

    // public int backgroundColor; 

/** 
*/ 

    public MyView(Context c) 
    { 
     super(c); 
     /*if (Draw.selectedImagePath == null) {*/ 
     setFocusable(true); 
     setFocusableInTouchMode(true);  
      // Figure out how this works. Seems odd that we set up a canvas and a bitmap. 
      // I don't see how it connects to what shows on screen.  
      mBitmap = Bitmap.createBitmap(Draw4FunMain.WW, Draw4FunMain.WH, Bitmap.Config.ARGB_8888); 
      mCanvas = new Canvas(mBitmap); 
      mPath = new Path(); 
      mBitmapPaint = new Paint(Paint.DITHER_FLAG); 
      // mCanvas.setBackgroundResource(0xFFFFFFFF); 
      if (Draw.imageBackgroundEraser == null) { 
       mCanvas.drawColor (Color.WHITE); 
      } else { 
       mCanvas.drawColor (Color.TRANSPARENT); 
      } 
      mCanvas.drawColor(Color.TRANSPARENT); 
    } 

    public MyView (Context c, int color) 
    { 
     super(c); 
     setFocusable(true); 
     setFocusableInTouchMode(true);  
      mBitmap = Bitmap.createBitmap(Draw.WW, Draw.WH, Bitmap.Config.ARGB_8888); 
      mCanvas = new Canvas(mBitmap); 
      mPath = new Path(); 
      mBitmapPaint = new Paint(Paint.DITHER_FLAG); 
      mCanvas.drawColor (color); 

    } 

/** 
*/ 
// Methods 

/** 
*/ 
@Override protected void onSizeChanged(int w, int h, int oldw, int oldh) 
{ 
    super.onSizeChanged(w, h, oldw, oldh); 
} 

/** 
*/ 
@Override protected void onDraw(Canvas canvas) 
{ 

     // canvas.drawColor(Color.TRANSPARENT); 

      canvas.drawBitmap(mBitmap, 0, 0, null); 

      for (Path p : paths){ 
       canvas.drawPath(p, Draw.mPaint); 
       //System.out.println("p-->" + p); 
      // System.out.println("Draw.mPaint-->" + Draw4FunMain.mPaint); 
      } 
      canvas.drawPath(mPath, Draw.mPaint); 

} 

/** 
*/ 
    private float mX, mY; 
    private static final float TOUCH_TOLERANCE = 4; 

/** 
*/ 
    private void touch_start(float x, float y) { 
     mPath.reset(); //------------------------- 
     mPath.moveTo(x, y); 
     mX = x; 
     mY = y; 
    } 
/** 
*/ 
    private void touch_move(float x, float y) { 
     float dx = Math.abs(x - mX); 
     float dy = Math.abs(y - mY); 
     if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) { 
      mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 
      mX = x; 
      mY = y; 
     } 
    } 
/** 
*/ 
    private void touch_up() { 
     mPath.lineTo(mX, mY); 
     // commit the path to our offscreen 
     mCanvas.drawPath(mPath, Draw.mPaint); 
     // kill this so we don't double draw 
     mPath.reset(); 

     paths.add(mPath); 
     mPath = new Path(); 
     System.out.println("path-->" + paths); 
     System.out.println("size-->" + paths.size()); 
    } 

/** 
*/ 
    public void onClickUndo() { 
     if (paths.size()>0) 
     { 
      undonePaths.add(paths.remove(paths.size()-1)); 
      invalidate(); 
     } 
     else 
     { 

     } 
     //toast the user 
    } 

    public void onClickRedo(){ 
     if (undonePaths.size()>0) 
     { 
      paths.add(undonePaths.remove(undonePaths.size()-1)); 
      invalidate(); 
     } 
     else 
     { 

     } 
    } 

@Override public boolean onTouchEvent(MotionEvent event) { 
     float x = event.getX(); 
     float y = event.getY(); 

     switch (event.getAction()) { 
      case MotionEvent.ACTION_DOWN: 
       touch_start(x, y); 
       invalidate(); 
       break; 
      case MotionEvent.ACTION_MOVE: 
       touch_move(x, y); 
       invalidate(); 
       break; 
      case MotionEvent.ACTION_UP: 
       touch_up(); 
       invalidate(); 
       break; 
     } 
     return true; 
    } 

} // end MyView 

错误------

11-14 14:55:39.022: E/AndroidRuntime(1728): FATAL EXCEPTION: main 
11-14 14:55:39.022: E/AndroidRuntime(1728): java.lang.IllegalStateException: Could not execute method of the activity 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.view.View$1.onClick(View.java:3591) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.view.View.performClick(View.java:4084) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.view.View$PerformClick.run(View.java:16966) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.os.Handler.handleCallback(Handler.java:615) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.os.Handler.dispatchMessage(Handler.java:92) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.os.Looper.loop(Looper.java:137) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.app.ActivityThread.main(ActivityThread.java:4899) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at java.lang.reflect.Method.invoke(Method.java:511) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at dalvik.system.NativeStart.main(Native Method) 
11-14 14:55:39.022: E/AndroidRuntime(1728): Caused by: java.lang.reflect.InvocationTargetException 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at java.lang.reflect.Method.invoke(Method.java:511) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at android.view.View$1.onClick(View.java:3586) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  ... 11 more 
11-14 14:55:39.022: E/AndroidRuntime(1728): Caused by: java.lang.NullPointerException 
11-14 14:55:39.022: E/AndroidRuntime(1728):  at com.draw.Draw4FunMain.onClick(Draw.java:246) 
11-14 14:55:39.022: E/AndroidRuntime(1728):  ... 14 more 

Answer 1

您的logCat指出您的代码行246上有一个NullPointerException。我会认为是这些行：

public void onClick(View view){ 
    switch (view.getId()){ 
    case R.id.undoBtn: 
     mView.onClickUndo(); 
    break; 

    case R.id.redoBtn: 
     mView.onClickRedo(); 
    break; 

的问题是，你没有初始化mView。在onCreate中，代替初始化本地变量myView。将该实例指定给mView应该可以解决您的问题。

Answer 2

是的。我也认为Paul-Jan是正确的。以下行

final MyView myView = new MyView(this); 

在Draw.java中的onCreate方法应该像刚刚那样更正。

myView = new MyView(this);