EditText和Paint一起在Android中像Note +一样

Question

我想开发一个像Note +这样的应用程序。此应用程序会自动安装在某些型号的手机中，如Samsung Note 5。 在此应用程序中，用户可以在EditText中输入Text并将输入模式更改为graphic，并通过手指在文本上绘制线条。 用户可以通过单击工具栏将模式更改为文本/图形。

我在图形模式下绘制线条的代码（Canvas）：

package com.note.vastac;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class MyDrawView extends View {
    public Bitmap  mBitmap;
    public Canvas  mCanvas;
    private Path    mPath;
    private Paint   mBitmapPaint;
    private Paint   mPaint;


    public MyDrawView(Context c, AttributeSet attrs) {
        super(c, attrs);

        mPath = new Path();
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(9);

    }


    @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.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;
    }

    public Bitmap getBitmap()
    {
        this.setDrawingCacheEnabled(true);  
        this.buildDrawingCache();
        Bitmap bmp = Bitmap.createBitmap(this.getDrawingCache());   
        this.setDrawingCacheEnabled(false);

    return bmp;
    }

    public void clear(){
        mBitmap.eraseColor(Color.TRANSPARENT);
        invalidate();
        System.gc();
    }
}

然后使用MyDrawView类将其包含到xml文件中：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Test">

    <com.note.vastac.MyDrawView
        android:id="@+id/draw"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
    </com.note.vastac.MyDrawView>
    <Button
        android:id="@+id/btnTextMode"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:text="Text" >
    </Button>
    <Button
        android:id="@+id/btnGraphicMode"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Graphic" >
    </Button>

</RelativeLayout>

问题是：如何从图形（手指画线）到文本（通过键盘输入文字）更改模式？