blocks|key|1659425|text|在油漆之前，先打个g.clearRect(0,0，w，h)电话。这将移除指定区域中的所有内容，并且不会在前一帧的基础上绘制。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1659426|您可能需要应用一些双重缓冲技术，因为您的屏幕将轻微闪烁，因为清除。|1659427|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/1.4.2/docs/api/java/awt/Graphics.html#clearRect%2528int,%2520int,%2520int,%2520int%2529^0|9|K|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

Before you do your paint, make a <a href="http://docs.oracle.com/javase/1.4.2/docs/api/java/awt/Graphics.html#clearRect%28int,%20int,%20int,%20int%29" rel="nofollow">g.clearRect(0,0,w,h)</a> call.
This will remove everything in the specified area, and you won't be drawing on top of the previous frame.

You may want to apply some double buffering techniques since your screen will flash slightly due to the clear.

blocks|key|1181524|text|类似的问题|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1181525|​|1181526|📷|atomic|offset|length|1181527|地址为这里|1181528|1181529|1181530|还要注意，"Swing程序应该覆盖paintComponent()而不是覆盖paint().“-https://www.oracle.com/technetwork/java/index.html#callbacks。|style|CODE|1181531|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/12bf308cfd94df1015d66506953d82b0.png|imageAlt|1|LINK|MUTABLE|url|https://stackoverflow.com/questions/2163544/re-paint-on-translucent-frame-panel-component/2166500#2166500|2|https://developer.qcloudimg.com/http-save/yehe-900000/e2c15de84fc9a2ebf33ba563c3b069ab.png|3|https://www.oracle.com/technetwork/java/index.html#callbacks^0|0|0|0|1|0|0|3|2|1|0|0|0|1|2|0|H|G|12|7|1C|1O|3|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|19|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1A|8|@]|9|@$G|1B|H|1C|1|1D]]|A|$]]|$1|I|3|J|5|6|7|1E|8|@]|9|@$G|1F|H|1G|1|1H]]|A|$]]|$1|K|3|C|5|6|7|1I|8|@]|9|@]|A|$]]|$1|L|3|E|5|F|7|1J|8|@]|9|@$G|1K|H|1L|1|1M]]|A|$]]|$1|M|3|N|5|6|7|1N|8|@$G|1O|H|1P|O|P]|$G|1Q|H|1R|O|P]]|9|@$G|1S|H|1T|1|1U]]|A|$]]|$1|Q|3|-4|5|6|7|1V|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X|Y|-4]]|Z|$5|10|U|11|A|$12|13]]|14|$5|T|U|V|A|$W|15|Y|-4]]|16|$5|10|U|11|A|$12|17]]]]

A similar problem

<a href="https://i.stack.imgur.com/X8iqb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X8iqb.png" alt="image before"></a>


is addressed <a href="https://stackoverflow.com/questions/2163544/re-paint-on-translucent-frame-panel-component/2166500#2166500">here</a>

<a href="https://i.stack.imgur.com/Kj8ds.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Kj8ds.png" alt="image after"></a>


Note also, "Swing programs should override <code>paintComponent()</code> instead of overriding <code>paint()</code>."—<a href="https://www.oracle.com/technetwork/java/index.html#callbacks" rel="nofollow noreferrer">Painting in AWT and Swing: The Paint Methods</a>.

I am currently developing a kiosk style Java program to display weather, time, forecast etc. Here is a shot of what the program should look like (screenshot taken before the time updated)
<img src="https://i.stack.imgur.com/5a2HJ.jpg" alt="Image showing required output before the graphical error" />
The various sections are created as JPanels with the <code>paintComponent()</code> method overridden. They draw in a gradient header and a semitransparent background. However, when I change the content of one of these panels, the previous content is left behind, rather than being removed. An example is shown below:
As you can see, when the time changed from 11:51 to 11:52, the numbers overlapped, and the background became lighter (because the semitransparent background was redrawn over it)
<h2>The Graphical Error</h2>
<img src="https://i.stack.imgur.com/JhmDv.png" alt="Image showing the graphical error" />
What should I do to prevent this overlap? Ultimately, I would prefer to not have to redraw the entire screen when an individual panel updates it's contents. I would prefer to only redraw that particular section. It would be easy to repaint the background, and then all the components within.
<h1>Update</h1>
Several answers involve clearing the area to be drawn. Whether I use <code>g.clear()</code> or <code>AlphaComposite.CLEAR</code> it erases the background image. this can be seen in the following image. Perhaps if I could copy the background before I clear the area, I could repaint that section of the background, then layer the other images appropriately. Thoughts?
<img src="https://i.stack.imgur.com/N8wU9.png" alt="enter image description here" />
<h1>Update 2</h1>
An answer was submitted which shows a complete working example of a timer laid over a transparent panel and a background. This is very useful, however, I am not painting my sub-componenets manually. The time, weather icons and temperatures are all JLabels laid out over the semi-transparent panel. I would prefer to not have to paint the individual components manually.

Java Transparency rendering error

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我目前正在开发一个kiosk风格的Java程序来显示天气、时间、天气预报等。下面是这个程序应该是什么样子的截图(截图是在更新之前拍摄的)。​​各个部分被创建为JPanels，paintComponent()方法被重写。他们画一个渐变头和半透明的背景。但是，当我更改其中一个面板的内容时，先前的内容将被抛在后面，而不是被删...

问Java透明呈现错误
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