当Android计算视图的宽度和高度时 [英] When android calculate width and height of views

问题描述

我通过代码创建视图层次结构，然后在活动"中使用像参数一样的根视图进行 setContentView().

I create my hierarchy of views by code, and then I do setContentView()in the Activity with my root view like argument.

我需要在运行时知道一个视图的宽度和高度，但是如果我执行 getWidth()或 getHeight()，我将得到0.如果我等待几秒钟我得到正确的宽度或高度.

I need know width and height of one view in runtime but if i do getWidth() or getHeight(), i get 0. If i wait a few seconds i get the correct width or height.

我只想知道android在什么时候计算视图的宽度/高度.我的代码不是很出色

I only want to know in what moment android calculate width / height of views. My code isn't outstanding

谢谢！

推荐答案

这是因为尚未在 onCreate()中计算布局.因此，您需要添加 GlobalLayoutListener 来了解何时已计算布局并将其放置在屏幕中.

This is because in onCreate() the layouts haven't been calculated yet. So you need to add a GlobalLayoutListener to know when layouts has been calculated and placed in screen.

final View view = findViewById(R.id.root);
ViewTreeObserver vto = view.getViewTreeObserver();
            vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
                @Override
                public void onGlobalLayout() {
                    ViewTreeObserver vto = view.getViewTreeObserver();
                    vto.removeGlobalOnLayoutListener(this);
                }
            });

其中root是根布局(即LinearLayout，RelativeLayout).用@ + id/root分配您的根布局.

Where root is the root layout (LinearLayout, RelativeLayout i.e). Assign your root layout with the @+id/root.

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