TextInputLayout错误文本右对齐失效问题求助

问题背景 #

需将Material Components的TextInputLayout错误文本显示在右侧，尝试过以下两种方式但均未生效：

1. 样式配置：在errorTextAppearance中设置android:textAlignment="viewEnd"
2. 自定义控件：通过反射获取内部mErrorView并修改其重力属性

尝试过的样式代码 #

<style name="Theme.Input" parent="Widget.MaterialComponents.TextInputLayout.OutlinedBox">
    <item name="hintEnabled">false</item>
    <item name="boxCornerRadiusBottomEnd">@dimen/input_box_corner_radius</item>
    <item name="boxCornerRadiusBottomStart">@dimen/input_box_corner_radius</item>
    <item name="boxCornerRadiusTopEnd">@dimen/input_box_corner_radius</item>
    <item name="boxCornerRadiusTopStart">@dimen/input_box_corner_radius</item>
    <item name="errorEnabled">true</item>
    <item name="errorTextColor">@color/red</item>
    <item name="boxStrokeErrorColor">@color/red</item>
    <item name="android:textColor">@color/colorInputText</item>
    <item name="iconEndPadding">@dimen/std_16dp</item>
    <item name="errorTextAppearance">@style/Theme.EZazi.Input.Error</item>
    <item name="android:textSize">@dimen/input_inner_size</item>
    <item name="boxStrokeWidth">@dimen/input_stroke_size</item>
    <item name="boxStrokeWidthFocused">@dimen/input_stroke_size</item>
</style>

<style name="Theme.Input.Error" parent="TextAppearance.Design.Error">
    <item name="android:textColor">@color/red</item>
    <item name="android:textSize">@dimen/caption</item>
    <item name="android:textAlignment">viewEnd</item>
</style>

尝试过的自定义控件代码 #

public class RightAlignErrorTextInputLayout extends TextInputLayout {
    public RightAlignErrorTextInputLayout(@NonNull Context context) {
        super(context);
        init();
    }

    public RightAlignErrorTextInputLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public RightAlignErrorTextInputLayout(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init(){
        setTextAlignment(View.TEXT_ALIGNMENT_VIEW_END);
    }

    @Override
    public void setErrorEnabled(boolean enabled) {
        super.setErrorEnabled(enabled);

        if (!enabled) {
            return;
        }

        try {
            Field errorViewField = TextInputLayout.class.getDeclaredField("mErrorView");
            errorViewField.setAccessible(true);
            TextView errorView = (TextView) errorViewField.get(this);
            if (errorView != null) {
                errorView.setGravity(Gravity.END);
                LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
                params.gravity = Gravity.END;
                errorView.setLayoutParams(params);
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}

可行解决方案 #

方案一：官方API（推荐） #

Material Components 1.4.0及以上版本新增了errorGravity属性，直接在布局或样式中配置即可实现错误文本右对齐，无需自定义控件或反射：

布局中直接设置

<com.google.android.material.textfield.TextInputLayout
    ...
    app:errorGravity="end" />

样式中全局配置

<style name="Theme.Input" parent="Widget.MaterialComponents.TextInputLayout.OutlinedBox">
    ...
    <item name="errorGravity">end</item>
</style>

若依赖版本低于1.4.0，建议升级Material库：

implementation 'com.google.android.material:material:1.4.0'

方案二：无反射自定义控件（兼容旧版本） #

针对无法升级库版本的场景，可通过遍历子视图找到错误文本控件，修改其布局属性实现右对齐，避免依赖内部私有字段：

public class RightAlignErrorTextInputLayout extends TextInputLayout {
    public RightAlignErrorTextInputLayout(@NonNull Context context) {
        super(context);
        setupErrorAlignment();
    }

    public RightAlignErrorTextInputLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        setupErrorAlignment();
    }

    public RightAlignErrorTextInputLayout(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setupErrorAlignment();
    }

    private void setupErrorAlignment() {
        getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                // 遍历子视图定位错误文本控件
                for (int i = 0; i < getChildCount(); i++) {
                    View child = getChildAt(i);
                    if (child instanceof TextView && child.getId() == com.google.android.material.R.id.textinput_error) {
                        TextView errorTv = (TextView) child;
                        // 设置文本右对齐
                        errorTv.setGravity(Gravity.END | Gravity.CENTER_VERTICAL);
                        // 让控件占满父容器宽度，确保文本右对齐生效
                        LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) errorTv.getLayoutParams();
                        params.width = LinearLayout.LayoutParams.MATCH_PARENT;
                        errorTv.setLayoutParams(params);
                        // 移除监听避免重复执行
                        getViewTreeObserver().removeOnGlobalLayoutListener(this);
                        break;
                    }
                }
            }
        });
    }
}

内容的提问来源于stack exchange，提问作者Android Leo