(안드로이드) 그림판 저장기능 오류.. 도와주세요!

Question

지금 저장기능을 넣어보았는데 기능 버튼을 누르면 다시 초기화면으로 돌아가기만 하고 저장은 안되네요 어떻게 해야할까요..? 도와주세요!

public class FirstActivity extends AppCompatActivity {

    Button btn1, btn2, btn3, btn4, btn5, btn6;
    Bitmap mBitmap;
    Canvas mCanvas;
    Path mPath;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(this));
        getSupportActionBar().hide();


        LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        final View v = inflater.inflate(R.layout.activity_first,null);
        addContentView(v , new FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT,FrameLayout.LayoutParams.MATCH_PARENT));

        btn1 = v.findViewById(R.id.button);
        btn2 = v.findViewById(R.id.button2);
        btn3 = v.findViewById(R.id.button3);
        btn4 = v.findViewById(R.id.button4);
        btn5 = v.findViewById(R.id.button5);
        btn6 = v.findViewById(R.id.button6);

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                colorChanged(0xFFFFFFFF);
                mPaint.setStrokeWidth(45);
            }
        });

        btn2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                colorChanged(0xFFFF0000);
                mPaint.setStrokeWidth(15);
            }
        });

        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                colorChanged(0xFF000000);
                mPaint.setStrokeWidth(15);
            }
        });

        btn4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mBitmap.eraseColor(0x00000000);
            }
        });
        btn5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                 String strFilePath = "/storage/emulated/0/Pictures/Screenshots";
                 String fileName = "screen";
                 SaveBitmapToFileCache(mBitmap,strFilePath,fileName);

            }
        });
        btn6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            }
        });

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFFFFAAAA);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(15);
        mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 },
                0.4f, 6, 3.5f);
        mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL);
    }
    private Paint       mPaint;
    private MaskFilter  mEmboss;
    private MaskFilter mBlur;

    public void colorChanged(int color) {
        mPaint.setColor(color);
    }

    public class MyView extends View {

        private static final float MINP = 0.25f;
        private static final float MAXP = 0.75f;
        Paint mBitmapPaint;

        public MyView(Context c) {
            super(c);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        }

        public MyView(Context c , AttributeSet att){
            super(c , att);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        }

        public MyView(Context c , AttributeSet att , int ref){
            super(c , att , ref);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
            mCanvas = new Canvas(mBitmap);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            canvas.drawColor(0x00000000);
            canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
            canvas.drawPath(mPath, 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);
            mCanvas.drawPath(mPath, mPaint);
            mPath.reset();
        }

        @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;
        }
    }

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 public static void SaveBitmapToFileCache(Bitmap bitmap, String strFilePath, String filename) {

     File file = new File(strFilePath);

     if (!file.exists()) {
         file.mkdirs();
     }

     File fileCacheItem = new File(strFilePath + filename);
     OutputStream out = null;

     try {

         fileCacheItem.createNewFile();
         out = new FileOutputStream(fileCacheItem);
         bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);

     } catch (Exception e) {
         e.printStackTrace();
     } finally {
         try {
             out.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }
    //ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ
}