大家好:
我想做android的習字版
讓使用者可以寫字練習
我現在已經弄出畫板了
但遇到一些問題
(1)我希望我的畫板是100X100就好，不要占全部的介面(我其他地方還要放單字)

   vBitmap = Bitmap.createBitmap(100, 100, Bitmap.Config.RGB_565);

我都設定了還是全版面.....
(2)我想做浮水印，但目前研究不出來浮水印怎麼做
想做如下圖

以下是程式碼:MainActivity

public class MainActivity extends AppCompatActivity {
    Panel mPanel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mPanel = new Panel(this);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        setContentView(mPanel);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

panel.java

class Panel extends View {
    List<PointF> points=new ArrayList<PointF>();

    Bitmap vBitmap;
    Canvas vBitmapCanvas;
    Paint mpaint = new Paint();

    public Panel(Context context) {
        super(context);
        mpaint.setColor(Color.BLUE);
        mpaint.setStyle(Paint.Style.STROKE);
        mpaint.setStrokeWidth(10);
        //設定bitmap大小
        vBitmap = Bitmap.createBitmap(100, 100, Bitmap.Config.RGB_565);
        vBitmapCanvas = new Canvas(vBitmap);
        vBitmapCanvas.drawColor(Color.WHITE);

    }
    @Override
    public void onDraw (Canvas canvas){
        super.onDraw(canvas);
        for (int i = 1; i < points.size(); i++) {
            PointF p1 = points.get(i - 1);
            PointF p2 = points.get(i);
            if(abs(p1.x-p2.x)<50 && abs(p1.y-p2.y)<50) {
                canvas.drawLine(p1.x, p1.y, p2.x, p2.y, mpaint);
                vBitmapCanvas.drawLine(p1.x, p1.y, p2.x, p2.y, mpaint);
            }
        }
    }

    @Override
    public boolean onTouchEvent (MotionEvent event){
        for (int i = 0; i < event.getHistorySize(); i++) {
            points.add(new PointF(event.getHistoricalX(i), event.getHistoricalY(i)));
        }
        Panel.this.invalidate();
        return true;
    }

}

以上，謝謝大家

進度更新:
報告個為大大，我已經可以調正畫板大小，接下來就是想怎麼讓畫板有浮水印了...
若有經驗的大大拜託提供意見和參考，謝謝~