如何在Android的画的时候屏蔽掉一个简单的区域？ [英] How to mask out a simple region when painting in Android?
问题描述
下面是一个简单的描述：想象一下，我给绘制在墙上的照片视图类，我想用切出一个窗口中绘制它。假设我扩展该视图类并覆盖其dispatchDraw（）方法来做到以下几点。首先绘制背景（如果有），以透过窗户可以看到。接下来，我想以某种方式掩盖了矩形窗口区域，然后调用super.dispatchDraw（）。最后，我想卸下面具，绘制站在窗口，使他们画了背景和墙壁都一个人。我怎样才能做到这一点？
下面是一些code，这似乎接近我所需要的：
@覆盖
保护无效dispatchDraw（帆布进入）{
INT W = into.getWidth（）;
INT H = into.getHeight（）;
INT W3 = W / 3;
INT H3 = H / 3;
into.drawLine（0，0，W，H，mPaint）;
保护区=新地区（W / 3，H / 3，2 * W / 3，2 * H / 3）;
into.cli pregion（保护，Op.INTERSECT）;
into.drawColor（Color.MAGENTA）; //或super.dispatchDraw（）在这里。
}
这给了我这样的：
这是那种我想要的对面。注意评为code上面的保护区域。我想品红色填充到的在该地区除了的无处不在发生。具体来说，就是我希望看到的是这样的：
在窗口的比喻，我应该再在一个位置，以解除限制，并绘制重叠两个窗口，墙上的正常方式的人或东西。
编辑：这是拉杰什CP答案的简化工作版本。我还添加了绘制在一切红色的前台的条纹，最后才能证明我可以删除限制以及添加它们。拉杰什谢谢！
公共类MaskTest延伸活动{ @覆盖
保护无效的onCreate（捆绑savedInstanceState）{
super.onCreate（savedInstanceState）;
的setContentView（新ClippView（getApplicationContext（）））;
} 私有类ClippView扩展视图{
私人油漆line_paint =新的油漆（）;
私人油漆strip_paint =新的油漆（）; 公共ClippView（上下文的背景下）{
超级（上下文）;
line_paint.setColor（Color.GRAY）;
line_paint.setStrokeWidth（20）;
strip_paint.setColor（Color.RED）;
} @覆盖
保护无效的onDraw（帆布油画）{
super.onDraw（画布）;
INT W = canvas.getWidth（）;
INT H = canvas.getHeight（）;
INT W3 = W / 3;
INT H3 = H / 3;
//此行再presents一些未知的情况下，我们绘制了过来。
canvas.drawLine（0，0，W，H，line_paint）;
//保护再presents一些区域，直到希望不是油漆过。
保护区=新区域（W3，H3，2 * W / 3，2 * H / 3）;
canvas.cli pregion（保护，Op.DIFFERENCE）;
//油漆品红在整个画布，避免受保护区域。
canvas.drawColor（Color.MAGENTA）;
//删除受保护的区域。
所有地区=新区域（0，0，W，H）;
canvas.cli pregion（所有，Op.UNION）;
//画一个广阔的应用前景条在整个画布。
canvas.drawRect（重量/ 2 - W / 20，0，W / 2 + W / 20，小时，strip_paint）;
}
}
}
公共类ClippView扩展视图{
民营涂料粉刷=新的油漆（）; 公共ClippView（上下文的背景下）{
超级（上下文）;
}
私人保护区;
/ *
*（非Javadoc中）
* @see android.view.View＃的onDraw（android.graphics.Canvas）
* @since 2013年4月12日
* @author rajeshcp
* /
@覆盖
保护无效的onDraw（帆布油画）{
super.onDraw（画布）;
// view.buildDrawingCache（）;
INT W = canvas.getWidth（）;
INT H = canvas.getHeight（）;
INT W3 = W / 3;
INT H3 = H / 3;
canvas.drawLine（0，0，W，H，油漆）;
保护=（保护== NULL）？新的地区（W3，H3，2 * W / 3，2 * H / 3）：保护;
canvas.cli pregion（保护，Op.DIFFERENCE）;
canvas.drawColor（Color.MAGENTA）;
}}
为此，我想这是你想要的。
Here is a simplified description: Imagine that I'm given a View class that draws a picture of a wall and I want to draw it with a window cut out. Assume that I extend that View class and override its dispatchDraw() method to do the following. First draw the background if any to be seen through the window. Next I want to mask out the rectangular window region somehow and then call super.dispatchDraw(). Finally I want to remove the mask and draw a person standing at the window so that they are painted over both the background and the wall. How can I do this?
Here is some code that seems close to what I need:
@Override
protected void dispatchDraw(Canvas into) {
int w = into.getWidth();
int h = into.getHeight();
int w3 = w / 3;
int h3 = h / 3;
into.drawLine(0, 0, w, h, mPaint);
Region protect = new Region(w / 3, h / 3, 2 * w / 3, 2 * h / 3);
into.clipRegion(protect, Op.INTERSECT);
into.drawColor(Color.MAGENTA); // or super.dispatchDraw() here.
}
That gives me this:
Which is sort of the opposite of what I want. Notice the Region named "protect" in the code above. I want the magenta fill to happen everywhere except in that region. Specifically, what I want to see is this:
In the analogy of the window, I should then be in a position to remove the restriction and draw a person or something in the normal way that overlaps both the window and the wall.
EDIT: Here is a simplified working version of the answer by Rajesh CP. I also added a red "foreground" stripe drawn over everything at the end to show that I can remove the restriction as well as add them. Thanks Rajesh!
public class MaskTest extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new ClippView(getApplicationContext()));
}
private class ClippView extends View {
private Paint line_paint = new Paint();
private Paint strip_paint = new Paint();
public ClippView(Context context) {
super(context);
line_paint.setColor(Color.GRAY);
line_paint.setStrokeWidth(20);
strip_paint.setColor(Color.RED);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int w = canvas.getWidth();
int h = canvas.getHeight();
int w3 = w / 3;
int h3 = h / 3;
// This line represents some unknown background that we are drawing over.
canvas.drawLine(0, 0, w, h, line_paint);
// 'protect' represents some area to not paint over until desired.
Region protect = new Region(w3, h3, 2 * w / 3, 2 * h / 3);
canvas.clipRegion(protect, Op.DIFFERENCE);
// Paint magenta over the entire canvas, avoiding the protected region.
canvas.drawColor(Color.MAGENTA);
// Remove the protected region.
Region all = new Region(0, 0, w, h);
canvas.clipRegion(all, Op.UNION);
// Draw a wide foreground strip over the entire canvas.
canvas.drawRect(w / 2 - w / 20, 0, w / 2 + w / 20, h, strip_paint);
}
}
}
public class ClippView extends View{
private Paint paint= new Paint();
public ClippView(Context context) {
super(context);
}
private Region protect;
/*
* (non-Javadoc)
* @see android.view.View#onDraw(android.graphics.Canvas)
* @since Apr 12, 2013
* @author rajeshcp
*/
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// view.buildDrawingCache();
int w = canvas.getWidth();
int h = canvas.getHeight();
int w3 = w / 3;
int h3 = h / 3;
canvas.drawLine(0, 0, w, h, paint);
protect = (protect == null) ? new Region(w3, h3, 2 * w / 3, 2 * h / 3) : protect;
canvas.clipRegion(protect, Op.DIFFERENCE);
canvas.drawColor(Color.MAGENTA);
}
}
Do this I think this is what you want.
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