How to achieve scraping effect in Android

A few months ago, when I was in touch with Android, I did a small project that used a scratch-like effect, and now I'm going to post the code

The first thing to do is something like eraser, then you can erase the handwriting on the paper.

/** * FileName:SplashActivity.java * * @desc eraser function, similar to scraping effect * @author HTP * @Date 20140311 * @version 1.00  
      
    * * public class Text_rubbler extends TextView {private float touch_tolerance;//fill distance, make the line more natural, soft, the smaller the value, the softer.  
    private final int bgcolor;  
    Bitmap private Bitmap Mbitmap;  
    Canvas private Canvas Mcanvas;  
    Brush private Paint Mpaint;  
    Private Path MPath;  
      
    Private float MX, my;  
      
    Private Boolean isdraw = false;  
      
    Public Text_rubbler {/** * @param contexts/super (context); Public Text_rubbler (context context, AttributeSet attrs, int defstyle) {Super (Contex  
        T, Attrs, Defstyle); bgcolor =//Attrs.getattributeintvalue ("http://schemas.android.com/apk/res/android",///"TextColor  
        ", 0xFFFFFF);  
    System.out.println ("Color:" +bgcolor);  
      
}    Public Text_rubbler (context, AttributeSet attrs) {Super (context, attrs); bgcolor =//Attrs.getattributeintvalue ("http://schemas.android.com/apk/res/android",///"TextColor  
        ", 0xFFFFFF);  
        System.out.println (bgcolor);   
    System.out.println (Attrs.getattributevalue ("http://schemas.android.com/apk/res/android",//"layout_width"));  
        } @Override protected void OnDraw (Canvas Canvas) {Super.ondraw (Canvas);  
            if (Isdraw) {Mcanvas.drawpath (MPath, mpaint);  
            Mcanvas.drawpoint (MX, My, mpaint);  
        Canvas.drawbitmap (mbitmap, 0, 0, NULL); /** * Open Erase function * * @param bgcolor * cover background color * @param paints 
     Trokewidth * Contact (RUBBER) Width * @param touchtolerance * padding distance, the smaller the value, the softer. */public void Beginrubbler (final int bgcolor, FInal int paintstrokewidth, float touchtolerance) {touch_tolerance = touchtolerance;  
        Set Brush Mpaint = new Paint ();  
        Mpaint.setalpha (0); Brush across the traces will become transparent color mpaint.setcolor (color.black);  
        This cannot be a transparent color mpaint.setxfermode (new Porterduffxfermode (PorterDuff.Mode.DST_OUT));  
        or//Mpaint.setalpha (0);  
      
        Mpaint.setxfermode (New Porterduffxfermode (PorterDuff.Mode.DST_IN));  
        Mpaint.setantialias (TRUE);  
        Mpaint.setdither (TRUE);  
        Mpaint.setstyle (Paint.Style.STROKE); Mpaint.setstrokejoin (Paint.Join.ROUND); Front rounded corner mpaint.setstrokecap (Paint.Cap.ROUND); Posterior rounded corner mpaint.setstrokewidth (paintstrokewidth);  
        Pen wide//Mark MPath = new Path ();  
        ; Overlay//if (Getlayoutparams (). width = layoutparams.fill_parent) {////} MBITMA p = Bitmap.createbitmap (GetlaYoutparams (). Width, getlayoutparams (). height, config.argb_8888);  
      
        Mcanvas = new Canvas (MBITMAP);  
        Mcanvas.drawcolor (bgcolor);  
    Isdraw = true; @Override public boolean ontouchevent (Motionevent event) {if (!isdraw) {retur  
        n true; Switch (event.getaction ()) {case Motionevent.action_down://Contact Press//touchdown (event.  
            GETRAWX (), Event.getrawy ());  
            Touchdown (Event.getx (), event.gety ());  
            Invalidate ();  
        Break  
            Case Motionevent.action_move://Contact Mobile Touchmove (Event.getx (), event.gety ());  
            Invalidate ();  
        Break  
            Case MOTIONEVENT.ACTION_UP://Contact Bounce TouchUp (Event.getx (), event.gety ());  
            Invalidate ();  
        Break  
        Default:break;  
    return true; } private void TouChdown (float x, float y) {mpath.reset ();  
        Mpath.moveto (x, y);  
        MX = x;  
    my = y;  
        } private void Touchmove (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 + Me)/2)  
            ;  
            MX = x;  
        my = y;  
        } private void TouchUp (float x, float y) {mpath.lineto (x, y);  
        Mcanvas.drawpath (MPath, mpaint);  
    Mpath.reset (); }  
      
}