XML : Attempt to invoke virtual method '' on a null object reference

I have problem with my first Android application, I am trying to do hand-signature. Code that display and draw line. Line is draw fine, but when I try clear canvas I get into error. Second problem is saving canvas image, I would like to just save it to ftp, I dont need full code, just some help how to store image to variable and than how to save it. Thank everyone for help.

Code failure is: "Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference" My activity code is:

      public class AndroidCanvasSignature extends Activity {                private CanvasView customCanvas;              @Override              protected void onCreate(Bundle savedInstanceState) {                  super.onCreate(savedInstanceState);                  setContentView(R.layout.activity_android_canvas_signature);                    customCanvas = (CanvasView) findViewById(R.id.signature_canvas);              }                public void clearCanvas(View v) {                  customCanvas.clearCanvas();              }                public void saveCanvas(View v){              View content = v;              content.setDrawingCacheEnabled(true);              content.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_HIGH);              Bitmap bitmap = content.getDrawingCache();              String path = Environment.getExternalStorageDirectory().getAbsolutePath();              File file = new File("../img/image.png");              FileOutputStream ostream;              try {                  file.createNewFile();                  ostream = new FileOutputStream(file);                  bitmap.compress(Bitmap.CompressFormat.PNG, 100, ostream);                  ostream.flush();                  ostream.close();                  Toast.makeText(getApplicationContext(), "image saved",Toast.LENGTH_LONG).show();              } catch (Exception e) {                  e.printStackTrace();                  Toast.makeText(getApplicationContext(), "error", Toast.LENGTH_LONG).show();              }              }          }    

and my view class: public class CanvasView extends View {

                      public int width;                      public int height;                      private Bitmap mBitmap;                      private Canvas mCanvas;                      private Path mPath;                      Context context;                      private Paint mPaint;                      private float mX, mY;                      private static final float TOLERANCE = 5;                          public CanvasView(Context c, AttributeSet attrs) {                            super(c, attrs);                          context = c;                            // we set a new Path                          mPath = new Path();                            // and we set a new Paint with the desired attributes                          mPaint = new Paint();                          mPaint.setAntiAlias(true);                          mPaint.setColor(Color.BLACK);                          mPaint.setStyle(Paint.Style.STROKE);                          mPaint.setStrokeJoin(Paint.Join.ROUND);                          mPaint.setStrokeWidth(4f);                      }                        // override onSizeChanged                      @Override                      protected void onSizeChanged(int w, int h, int oldw, int oldh) {                          super.onSizeChanged(w, h, oldw, oldh);                            // your Canvas will draw onto the defined Bitmap                          mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);                          mCanvas = new Canvas(mBitmap);                      }                        // override onDraw                      @Override                      protected void onDraw(Canvas canvas) {                          super.onDraw(canvas);                          // draw the mPath with the mPaint on the canvas when onDraw                          canvas.drawPath(mPath, mPaint);                      }                        // when ACTION_DOWN start touch according to the x,y values                      private void startTouch(float x, float y) {                          mPath.moveTo(x, y);                          mX = x;                          mY = y;                      }                        // when ACTION_MOVE move touch according to the x,y values                      private void moveTouch(float x, float y) {                          float dx = Math.abs(x - mX);                          float dy = Math.abs(y - mY);                          if (dx >= TOLERANCE || dy >= TOLERANCE) {                              mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);                              mX = x;                              mY = y;                          }                      }                        public void clearCanvas() {                          mPath.reset();                          invalidate();                      }                        // when ACTION_UP stop touch                      private void upTouch() {                          mPath.lineTo(mX, mY);                      }                        //override the onTouchEvent                      @Override                      public boolean onTouchEvent(MotionEvent event) {                          float x = event.getX();                          float y = event.getY();                            switch (event.getAction()) {                              case MotionEvent.ACTION_DOWN:                                  startTouch(x, y);                                  invalidate();                                  break;                              case MotionEvent.ACTION_MOVE:                                  moveTouch(x, y);                                  invalidate();                                  break;                              case MotionEvent.ACTION_UP:                                  upTouch();                                  invalidate();                                  break;                          }                          return true;                      }                  }