更改AppBarLayout高度编程Android中 [英] Change AppBarLayout height programatically in Android

问题描述

我想实现灵活的空间使用的图像模式，使用的本教程。

I'm trying to implement Flexible Space with image pattern, using this tutorial.

一切工作正常。

注意AppBarLayout的高度定义是192dp。

Notice the height definition of the AppBarLayout which is 192dp.

我想使画面的高度，而不是1/3，以符合<一个href=\"http://material-design.storage.googleapis.com/publish/material_v_4/material_ext_publish/0B6Okdz75tqQscXNQY3dNdVlYeTQ/patterns-scrolling-techniques_flex_space_image_xhdpi_003.webm\"相对=nofollow>谷歌这样的例子这里模式。

I'd like to make the height 1/3 of the screen instead, to match this google example for the pattern here.

下面是在活动的onCreate的code（布局XML是完全一样的教程）：

Here's the code in the activity's onCreate (the layout xml is exactly the same as in the tutorial):

AppBarLayout appbar = (AppBarLayout)findViewById(R.id.appbar);
float density = getResources().getDisplayMetrics().density;
float heightDp = getResources().getDisplayMetrics().heightPixels / density;
appbar.setLayoutParams(new CoordinatorLayout.LayoutParams(LayoutParams.MATCH_PARENT, Math.round(heightDp / 3)));

但由于某些原因，结果是不是我期待的。我看不到应用栏在所有使用code。 （不code时，高度显示了如预期，但它从XML的并且不能动态地设置）。

But for some reason, the result is not what I'm expecting. I can't see the app bar at all with this code. (without the code, the height shows as expected but it's from XML and can't be set dynamically).

推荐答案

做到这一点，而不是：

    AppBarLayout appbar = (AppBarLayout) findViewById(R.id.appbar);
    float heightDp = getResources().getDisplayMetrics().heightPixels / 3;
    CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)appbar.getLayoutParams();
    lp.height = (int)heightDp;

在原来的code我认为你计算在屏幕的1/3是错误的，但你还是应该看到的东西。这可能是因为在setLP（）中的LayoutParams.MATCH_PARENT未正确导入。总是首先声明视图类型，即CoordinatorLayout.LayoutParams，以确保公正。否则，它可以很容易使用Framelayout.LayoutParams，例如。

In your original code I think that you calculation for 1/3 of the screen was wrong, but you still should have seen something. It could be that the LayoutParams.MATCH_PARENT in the setLP() wasn't imported correctly. Always declare the view type first, i.e. CoordinatorLayout.LayoutParams just to make sure. Otherwise it can be easy to use a Framelayout.LayoutParams, for instance.

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