使用Android绘制自定义视图 [英] Drawing custom view using Android

问题描述

我正在我的应用程序中绘制一个自定义视图，该视图基本上将arguments(XML)作为要显示的文本，然后继续无限旋转它.

I am drawing a custom view in my application which basically takes arguments(XML) as the text to display and then keeps on rotating it infinitely.

在进行此控制时，我有一些疑问想问:

While I was making this control I had a few doubts which I want to ask:

• 我已经制作了两个我在 attrs.xml 文件中声明的可样式化属性.这些属性用于设置控件中使用的圆的宽度和宽度.我将在ondraw方法和onmeasure方法中使用这些值.我通过声明这些来运行我的程序，但是有一个错误要求我放置 android:width和android:height 属性.我的问题是，如果我已经在使用自定义属性定义视图的高度和宽度，为什么我需要那些

• I have made 2 of my stylable attributes which I have declared in the attrs.xml file. These attributes are to set the width and the width of the circle used in my control. These values I would use in the ondraw method and the onmeasure method. I ran my program by declaring just these but there was an error which asked me to put android:width and android:height attributes. My question is why would I need those if I am already using my custom attributes to define the height and the width of my view

我正在Mac上进行编码.现在，当我制作我的 attrs.xml 文件时，要显示通常由ctrl + space来获取的自动完成列表并没有显示出来.这是为什么.例如，我想知道我可以给自定义属性的format属性提供哪些值，就像我在下面进行降级处理一样:< attr name ="somename" format ="value我想通过自动填充功能查找的内容"> .为什么自动弹出功能没有弹出?当我制作一个.java文件时，它确实会弹出.

I am coding on a mac. Now when I was making my attrs.xml file, to get the autocomplete list which we usually get by ctrl+space was not showing up. Why is that. For e.g., i wanted to know what values can I give the format attribute of my custom attribute that like I am demostrating in the following: <attr name ="somename" format="value I wanted to find out through autocomplete"> . Why is the autocomplete not popping up? It does pop up when I am making a.java file.

在我的 ondraw()方法中，我想绘制一个圆.现在，为此，我需要圆心的坐标.所以我要做的是0，0.但这是不正确的.我希望圆位于它所在的父视图的中心.因此，如果我的视图处于层次结构中，我希望它尊重它.我想给出相对于父视图的坐标.现在发生的现象是它绘制在屏幕的左上角.这就是我所不想要的.我要怎么做才能做到这一点?

In my ondraw() method I wanted to draw a circle. Now for this I would require the co-ordinates of the center of the circle. So what I do is put 0, 0. But this is not correct. I want the circle to be at the center of the parent view it is in. So if my view is in a hierarchy I want it to respect that. I want to give the co-ordinates relative to the parent view. What is happeining right now is that it is being drawn at the top left corner of my screen. This is what I don't want. What do I do to achieve this?

推荐答案

如果我已经在使用自定义属性定义视图的高度和宽度，为什么还要使用这些属性?

why would I need those if I am already using my custom attributes to define the height and the width of my view?

这是因为Android需要知道如何以及在布局中放置视图的位置.您可以通过覆盖.

This is because Android needs to know how and where to put your view in the layout. You can implement your view to make use of your custom height/width requirements by overriding View.onMeasure() to return your own size parameters. You can then just set android:layout_width="wrap_content" android:layout_height="wrap_content" in your layout file.

为什么不弹出自动完成功能?当我制作一个.java文件时，它确实会弹出.

Why is the autocomplete not popping up? It does pop up when I am making a.java file.

Android xml文件的自动完成和自动文档实现充其量是不稳定的，因此它不起作用并不奇怪.我不知道有修复程序，而AFAIK是一个IDE错误.

Autocomplete and autodoc implementation for Android xml files is shaky at best, so it's not really surprising that it doesn't work. I'm not aware of a fix and AFAIK it's an IDE bug.

在我的ondraw()方法中，我想绘制一个圆圈.现在我需要中心的坐标圆圈.所以我要做的就是0，0.但是这是不正确的.我想要圈子在父视图的中心它在里面.所以，如果我的观点在我希望它尊重等级制度.一世想要给坐标相对转到父视图.什么是幸福现在是它被绘制在屏幕的左上角.这个是我不想要的我该怎么办实现这一目标?

In my ondraw() method I wanted to draw a circle. Now for this I would require the co-ordinates of the center of the circle. So what I do is put 0, 0. But this is not correct. I want the circle to be at the center of the parent view it is in. So if my view is in a hierarchy I want it to respect that. I want to give the co-ordinates relative to the parent view. What is happeining right now is that it is being drawn at the top left corner of my screen. This is what I don't want. What do I do to achieve this?

如果正确实现了onMeasure()，则相对于父级的坐标应已得到照顾.要获得视图的中心，请使用以下代码:

If you implemented onMeasure() correctly, the coordinates relative to parent should be taken care of already. To get the center of your view use the following code:

void onDraw(Canvas canvas)
{
int centerX = this.getWidth() / 2;
int centerY = this.getHeight()) / 2;
//..draw code here
}

修改
这是一个源代码示例，应该可以帮助您: http://mindtherobot.com/blog/272/android-custom-ui-making-a-vintage-thermometer/

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