Android实现刮刮乐示例分析

微信公众号有很多都做刮刮乐的活动，本文就实现了刮刮乐的效果，具体代码如下：

首先要做一个类似橡皮擦的东西吧，然后才能把纸上的笔迹擦除
 

/** 
   * filename: splashactivity.java 
   * 
   * @desc 橡皮擦功能，类似刮刮乐效果 
   * @author htp 
   * @date 20140311 
   * @version 1.00 
   */ 
  public class text_rubbler extends textview { 
   
    private float touch_tolerance; // 填充距离，使线条更自然，柔和,值越小，越柔和。 
   
    // private final int bgcolor; 
    // 位图 
    private bitmap mbitmap; 
    // 画布 
    private canvas mcanvas; 
    // 画笔 
    private paint mpaint; 
    private path mpath; 
    private float mx, my; 
   
    private boolean isdraw = false; 
   
    public text_rubbler(context context) { 
      /** 
       * @param context 上下文 
       */ 
      super(context); 
   
    } 
   
    public text_rubbler(context context, attributeset attrs, int defstyle) { 
      super(context, attrs, defstyle); 
      // bgcolor = 
      // attrs.getattributeintvalue("http://schemas.android.com/apk/res/android", 
      // "textcolor", 0xffffff); 
      // system.out.println("color:"+bgcolor); 
    } 
   
    public text_rubbler(context 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); 
      } 
    } 
   
    /** 
     * 开启檫除功能 
     * 
     * @param bgcolor 
     *      覆盖的背景颜色 
     * @param paintstrokewidth 
     *      触点（橡皮）宽度 
     * @param touchtolerance 
     *      填充距离,值越小，越柔和。 
     */ 
    public void beginrubbler(final int bgcolor, final int paintstrokewidth, 
        float touchtolerance) { 
      touch_tolerance = touchtolerance; 
      // 设置画笔 
      mpaint = new paint(); 
      // mpaint.setalpha(0); 
      // 画笔划过的痕迹就变成透明色了 
      mpaint.setcolor(color.black); // 此处不能为透明色 
      mpaint.setxfermode(new porterduffxfermode(porterduff.mode.dst_out)); 
      // 或者 
      // 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); // 前圆角 
      mpaint.setstrokecap(paint.cap.round); // 后圆角 
      mpaint.setstrokewidth(paintstrokewidth); // 笔宽 
   
      // 痕迹 
      mpath = new path(); 
      ; 
      // 覆盖 
      // if (getlayoutparams().width == layoutparams.fill_parent) { 
      // 
      // } 
      mbitmap = 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) { 
        return true; 
      } 
      switch (event.getaction()) { 
      case motionevent.action_down: // 触点按下 
        // touchdown(event.getrawx(),event.getrawy()); 
        touchdown(event.getx(), event.gety()); 
        invalidate(); 
        break; 
      case motionevent.action_move: // 触点移动 
        touchmove(event.getx(), event.gety()); 
        invalidate(); 
        break; 
      case motionevent.action_up: // 触点弹起 
        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 + my) / 2); 
        mx = x; 
        my = y; 
      } 
   
    } 
   
    private void touchup(float x, float y) { 
      mpath.lineto(x, y); 
      mcanvas.drawpath(mpath, mpaint); 
      mpath.reset(); 
    } 
   
  } 

接下来就是使用橡皮檫擦除了
 

  /** 
   * filename: rubbleract.java 
   * @desc  该类通过调用text_rubbler这个类将在activity上显示一片刮一刮的区域，可以出发触摸事件 
   * @author htp 
   * @date  20140312 
   * @version 1.00 
   */ 
   
   
  public class rubbleract extends activity { 
    // 刮开后文字显示 
    private textview tv_rubbler; 
    // 得到刮一刮的内容 
    private sentence msentence; 
    // 下一张 
    private textview tv_next; 
   
    @override 
    public void oncreate(bundle savedinstancestate) { 
      super.oncreate(savedinstancestate); 
   
      // setcontentview(new rubble(this,"谢谢惠顾",new rect(100, 200, 
      // 300,250),2,1f,14)); 
   
      // ///////////////////////////////////////// 
      setcontentview(r.layout.rubbler); 
      // 设置的颜色必须要有透明度。 
      ((text_rubbler) findviewbyid(r.id.rubbler)).beginrubbler(0xffffffff, 20, 
          1f);// 设置橡皮擦的宽度等 
      msentence = new sentence(); 
      // 随机初始化文字 
      tv_rubbler = (textview) findviewbyid(r.id.rubbler); 
      string str = msentence.getsentence(); 
      tv_rubbler.settext(str); 
   
      tv_next = (textview) findviewbyid(r.id.tv_next); 
   
      // 点击下一步 
      tv_next.setonclicklistener(new onclicklistener() { 
   
        @override 
        public void onclick(view v) { 
          // todo auto-generated method stub 
          string str = msentence.getsentence(); 
          tv_rubbler.settext(str); 
          ((text_rubbler) findviewbyid(r.id.rubbler))// 初始化状态 
              .beginrubbler(0xffffffff, 20, 1f); 
   
        } 
      }); 
   
    } 
   
    class rubble extends view { 
   
      private final int paint_stroke_width; 
      private final float touch_tolerance; // 填充距离，使线条更自然，柔和,值越小，越柔和。 
      private final int text_size; 
   
      private bitmap mbitmap; 
      // 画布 
      private canvas mcanvas; 
      // 画笔 
      private paint mpaint; 
      private path mpath; 
      private float mx, my; 
      private final int x, y, w, h; 
   
      private final rect touchrect; 
   
      public rubble(context context, string bgtext, rect rect, 
          int paintstrokewidth, float touchtolerance, int textsize) { 
        super(context); 
        setfocusable(true); 
        touchrect = rect; 
        w = rect.right - rect.left; 
        h = rect.bottom - rect.top; 
        x = rect.left; 
        y = rect.top; 
        text_size = textsize; 
        paint_stroke_width = paintstrokewidth; 
        touch_tolerance = touchtolerance; 
        setbackground(touchrect, bgtext); 
        initdrowtools(); 
   
      } 
   
      private void setbackground(rect rect, string bgtext) { 
        displaymetrics dm = new displaymetrics(); 
        dm = this.getresources().getdisplaymetrics(); 
   
        bitmap bitmap = bitmap.createbitmap(dm.widthpixels, 
            dm.heightpixels, config.argb_8888); 
        canvas canvas = new canvas(bitmap); 
   
        paint paint = new paint(); 
        paint.setcolor(0x88000000); 
        // paint.setstyle(style.stroke); 
        // paint.settextalign(align.center); 
        paint.settextsize(text_size); 
   
        // paint.settextscalex(1.5f); 
        canvas.drawcolor(color.white); 
        // 画字的坐标不好控制 
        int x = rect.left 
            + (rect.right - rect.left - bgtext.length() * text_size) 
            / 2; 
        int y = rect.top + (rect.bottom - rect.top - text_size) / 2; 
        // int y = 218+25; 
        canvas.drawtext(bgtext, x, y, paint); 
        drawable drawable = new bitmapdrawable(bitmap); 
        setbackgrounddrawable(drawable); 
      } 
   
      private void initdrowtools() { 
        // 设置画笔 
        mpaint = new paint(); 
        // mpaint.setalpha(0); 
        // 画笔划过的痕迹就变成透明色了 
        mpaint.setcolor(color.black); // 此处不能为透明色 
        mpaint.setxfermode(new porterduffxfermode(porterduff.mode.dst_out)); 
        // 或者 
        // 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); // 前圆角 
        mpaint.setstrokecap(paint.cap.round); // 后圆角 
        mpaint.setstrokewidth(paint_stroke_width); // 笔宽 
   
        // 痕迹 
        mpath = new path(); 
        ; 
   
        // 覆盖 
        mbitmap = bitmap.createbitmap(w, h, config.argb_8888); 
        mcanvas = new canvas(mbitmap); 
        mcanvas.drawcolor(0x88000000); 
   
      } 
   
      @override 
      protected void ondraw(canvas canvas) { 
        super.ondraw(canvas); 
        mcanvas.drawpath(mpath, mpaint); 
        // mcanvas.drawpoint(mx, my, mpaint); 
        canvas.drawbitmap(mbitmap, x, y, null); 
      } 
   
      @override 
      public boolean ontouchevent(motionevent event) { 
        system.out.print("x--" + event.getx()); 
        system.out.println("y--" + event.gety()); 
        if (!touchrect.contains((int) event.getx(), (int) event.gety())) { 
          return false; 
        } 
   
        switch (event.getaction()) { 
        // 触点按下 
        case motionevent.action_down: { 
          touchdown(event.getrawx(), event.getrawy()); 
          touchdown(event.getx() - touchrect.left, event.gety() 
              - touchrect.top); 
          invalidate(); 
          break; 
        } 
           
        case motionevent.action_move: // 触点移动 
          touchmove(event.getx() - touchrect.left, event.gety() 
              - touchrect.top); 
   
          invalidate(); 
          break; 
        case motionevent.action_up: // 触点弹起 
          touchup(event.getx() - touchrect.left, event.gety() 
              - touchrect.top); 
          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 + my) / 2); 
          mx = x; 
          my = y; 
        } 
   
      } 
   
      private void touchup(float x, float y) { 
        mpath.lineto(x, y); 
        mcanvas.drawpath(mpath, mpaint); 
        mpath.reset(); 
      } 
   
    } 
   
    /** 
     * 键盘事件，当按下back键的时候询问是否再按一次退出程序 
     */ 
    // 退出时间 
    private long exittime = 0; 
    @override 
    public boolean onkeydown(int keycode, keyevent event) { 
      if (keycode == keyevent.keycode_back 
          && event.getaction() == keyevent.action_down) { 
        if ((system.currenttimemillis() - exittime) > 2000) { 
          toast.maketext(getapplicationcontext(), "再按一次退出程序", 
              toast.length_short).show(); 
          exittime = system.currenttimemillis(); 
        } else { 
          finish(); 
          system.exit(0); 
   
        } 
        return true; 
      } 
      return super.onkeydown(keycode, event); 
    } 
   
  } 

实现效果如下：

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