java - 计算我 dp 出错的高度

Question

这里的主要问题是父布局是嵌套 ScrollView ，因此高度必须是换行内容 所以 View 就像第一张图片

what I want is to make the "don't have an account? register" TextView to be at the bottom of the screen so I calculate the height of my phone then the height of layout to subtract to subtract them and assign the result to the top margin of textview

这是我的代码

ViewTreeObserver observer = binding.parentConstraint.getViewTreeObserver();
        if (observer.isAlive()) {
            observer.addOnGlobalLayoutListener(() -> {
                DisplayMetrics displayMetrics = getContext().getResources().getDisplayMetrics();
                float parentViewHeightInDP = (int) (binding.parentConstraint.getHeight() / displayMetrics.density);
                if (getContext() != null) {
                    float heightInDP = displayMetrics.heightPixels / displayMetrics.density;

                    float distanceBetweenLayoutBottomAndParenBottom =  heightInDP - parentViewHeightInDP;
                    if (distanceBetweenLayoutBottomAndParenBottom > 32) {
                        if (topMargin == 0) {
                            topMargin = 1;
                            ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) binding.loginTextDontHaveAccount.getLayoutParams();
                            layoutParams.topMargin = Math.round(distanceBetweenLayoutBottomAndParenBottom);
                            Handler handler = new Handler();
                            handler.postDelayed(() -> {
                                binding.loginTextDontHaveAccount.requestLayout();                            }, 
50);
                    }
                }

但是我得到的结果

so my real question here is why there still some space here, I mean the TextView should be exactly at the bottom

Answer 1

我建议你将 NestedScrollView 设置为 subview 而不是父 View 。 将RelativeLayout设为父级，并使用layout_alignParentBottom将TextView设置在底部。像这样的东西。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.core.widget.NestedScrollView 
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:background="?android:colorBackground"
         android:clickable="true"
         android:fillViewport="true"
         android:focusable="true">

     <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <ImageView
                android:id="@+id/img1"
                android:layout_width="wrap_content"
                android:layout_height="650dp"
                android:background="@mipmap/ic_launcher" />

            <ImageView
                android:layout_width="match_parent"
                android:layout_height="650dp"
                android:layout_below="@+id/img1"
                android:background="@color/colorPrimary" />
        </LinearLayout>
    </RelativeLayout>
 </androidx.core.widget.NestedScrollView>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true" />
 </RelativeLayout>