英文:
How to get size of an image from xml in android
问题
我正在开发一个使用图像并且拥有约束布局的安卓应用程序。高度和宽度的属性被设置为“wrap-content”，意味着它们并非固定的。在该图像上，我正在使用圆来创建一个图表。为此，我需要知道图像的宽度和高度的确切值。我该如何从XML获取宽度和高度的值到Java中？
英文:
I am developing an android application that uses an image and has a constraint layout. The attributes for height and width are set to "wrap-content" meaning they are not fixed. On that image, I am creating a graph using circles. For that, I should know the exact values of the width and height of the image. How can I get the values of width and height from XML to Java?
答案1
得分: 1
你可以使用 getWidth 和 getHeight 在运行时获取任何视图（在本例中为 constraint layout）的尺寸。<br />
但要注意，在使用这两个方法之前，你必须确保视图（constraint layout）已经被创建，否则它会返回 0，这意味着你不能在 onCreate 中调用它们。<br />
因此，正确的做法是等待视图被创建，然后获取其尺寸。
像这样：
创建这个方法
public static void runJustBeforeBeingDrawn(final View view, final Runnable runnable) {
final OnPreDrawListener preDrawListener = new OnPreDrawListener() {
@Override
public boolean onPreDraw() {
view.getViewTreeObserver().removeOnPreDrawListener(this);
runnable.run();
return true;
}
};
view.getViewTreeObserver().addOnPreDrawListener(preDrawListener);
}
然后在需要获取尺寸时调用它
runJustBeforeBeingDrawn(yourView, new Runnable() {
@Override
public void run() {
// 在这里你可以安全地获取视图尺寸（使用“getWidth”和“getHeight”），并对其进行任何所需操作
}
});
与你的问题相关：<br />
View 的 getWidth() 和 getHeight() 返回 0<br />
在运行时确定 Android 视图的尺寸
英文:
You can use getWidth and getHeight to get dimensions of any view (in this case constraint layout) at runtime.<br />
But be carful, before using this two methods you have to make sure that the view (constraint layout) is already created, otherwise it gonna return 0, witch means you can't call them in onCreate.<br />
So the correct way to do it is to wait for the view to be created then get its size.
Like this :
create this method
public static void runJustBeforeBeingDrawn(final View view, final Runnable runnable) {
final OnPreDrawListener preDrawListener = new OnPreDrawListener() {
@Override
public boolean onPreDraw() {
view.getViewTreeObserver().removeOnPreDrawListener(this);
runnable.run();
return true;
}
};
view.getViewTreeObserver().addOnPreDrawListener(preDrawListener);
}
Then call it when u need to get the dimensions
runJustBeforeBeingDrawn(yourView, new Runnable() {
@Override
public void run() {
//Here you can safely get the view size (use "getWidth" and "getHeight"), and do whatever you wish with it
}
});
Related to your question :<br />
View's getWidth() and getHeight() returns 0<br />
Determining the size of an Android view at runtime
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