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类似于“by”,但适用于get/set方法以外的其他方法

kotlin

Damn Vegetables · 技术社区 · 3 年前

我只是刚刚发现了 by 关键词 class override fun suggestSelection(...} ,它似乎没有回来 fallback.suggestSelection(text, selectionStartIndex, selectionEndIndex, defaultLocales); . 如您所见,它所做的只是在中调用相同的方法 fallback 用同样的论点。这是唯一的办法还是有什么办法 退路

inner class MyTextClassfier(private val fallback:TextClassifier) : TextClassifier by fallback
{
    override fun suggestSelection(
        text: CharSequence,
        selectionStartIndex: Int,
        selectionEndIndex: Int,
        defaultLocales: LocaleList?
    ): TextSelection
    {
        return fallback.suggestSelection(text, selectionStartIndex, selectionEndIndex, defaultLocales);
    }

按以下要求添加完整代码。它需要Android Studio生成的默认Android项目结构。

主要活动。kt

package com.stackoverflow.test

import android.content.Context
import android.os.Bundle
import android.os.LocaleList
import android.util.Log
import android.view.textclassifier.TextClassification
import android.view.textclassifier.TextClassificationManager
import android.view.textclassifier.TextClassifier
import android.view.textclassifier.TextSelection
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity()
{
    override fun onCreate(savedInstanceState: Bundle?)
    {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val textClassificationManager = getSystemService(Context.TEXT_CLASSIFICATION_SERVICE) as TextClassificationManager;
        val defaultOne = textClassificationManager.textClassifier;
        val txt = findViewById<TextView>(R.id.textview1);
        txt.setTextClassifier(MyTextClassfier(defaultOne));
    }

    inner class MyTextClassfier(private val fallback:TextClassifier) : TextClassifier by fallback
    {
        override fun suggestSelection(
            text: CharSequence,
            selectionStartIndex: Int,
            selectionEndIndex: Int,
            defaultLocales: LocaleList?
        ): TextSelection
        {
            return fallback.suggestSelection(text, selectionStartIndex, selectionEndIndex, defaultLocales);
            //return TextSelection.Builder(0,0).build();
        }

        override fun classifyText(
            text: CharSequence,
            startIndex: Int,
            endIndex: Int,
            defaultLocales: LocaleList?
        ): TextClassification
        {
            //Selection ended. User has lifted his finger.
            Log.d("stack", "classifyText is called.");
            return TextClassification.Builder().build();
        }

    }
}

主要活动。xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        xmlns:app="http://schemas.android.com/apk/res-auto">
    <TextView
        android:id="@+id/textview1"
            android:text="@string/large_text"
            android:textAppearance="@style/TextAppearance.AppCompat.Large"
            android:textIsSelectable="true"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>

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