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android - 尝试使用 onSaveInstanceState 和 onRestoreSaveInstanceState 来保存我的活动状态，但它不起作用

问题描述

我正在尝试制作一个测验应用程序，以便当用户单击加号按钮时，它会将他们带到他们输入问题和答案的页面，然后他们可以保存并返回到上一页，其中有一个新按钮设置为问题的文本被创建。我已经对所有这些进行了编码和工作，除了如果用户想要编辑它可以保存问题/答案活动状态的部分。我尝试使用 onSaveInstanceState 和 onRestoreSaveInstanceState 但它根本没有保存活动。有人可以看到我做错了什么吗？这是我的代码：

主要活动：

    package com.example.quest

import android.app.Activity
import android.app.AlertDialog
import android.content.Intent
import android.graphics.Color
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.Gravity
import android.widget.Button
import android.widget.LinearLayout
import android.widget.TextView
import com.google.android.material.floatingactionbutton.FloatingActionButton

class MainActivity : AppCompatActivity() {
    private val questionActivityCode = 2
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        findViewById<FloatingActionButton>(R.id.btn2).setOnClickListener{
            startActivityForResult(Intent(this@MainActivity, SecondActivity::class.java), questionActivityCode)
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        if (requestCode == questionActivityCode && resultCode == Activity.RESULT_OK) {
            createNewButtonWithText(data?.getStringExtra("test") ?: "")
        }
    }

    private fun createNewButtonWithText(text: String)
    {
        val newbutton = Button(this@MainActivity)
        val layout = findViewById<LinearLayout>(R.id.mainlayout)
        newbutton.text = text
        newbutton.layoutParams = LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT)
        newbutton.width=1010
        newbutton.height=300
        newbutton.gravity = Gravity.CENTER
        newbutton.translationX= 65F
        newbutton.setTextColor(Color.parseColor("#FFFFFFFF"))
        newbutton.setBackgroundColor(Color.parseColor("#250A43"))
        layout.addView(newbutton)

        val inflator = layoutInflater
        val builder = AlertDialog.Builder(this)
        val intent = Intent(this@MainActivity, SecondActivity::class.java)

        newbutton.setOnClickListener{
            val dialogLayout = inflator.inflate(R.layout.text, null)
            with(builder) {
                setTitle(newbutton.text)
                setPositiveButton("Edit"){dialog, which ->
                    startActivity(intent)
                }
                setNegativeButton("Cancel"){dialog, which ->
                    Log.d("Main", "Negative button clicked")
                }
                setView(dialogLayout)
                show()
        }
    }
}}

第二个活动：

    package com.example.quest

import android.app.Activity
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.EditText
import com.google.android.material.floatingactionbutton.FloatingActionButton

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

        val question = findViewById<EditText>(R.id.question)

        findViewById<FloatingActionButton>(R.id.btn3).setOnClickListener{
            val questiontext = question.text.toString()

            val returnIntent = Intent()
            returnIntent.putExtra("test", questiontext)
            setResult(Activity.RESULT_OK, returnIntent)

            finish()
        }
    }
    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        Log.i("Instance State", "onSaveInstanceState")

        val question = findViewById<EditText>(R.id.question)
        val answer = findViewById<EditText>(R.id.answer)

        outState.putCharSequence("savedQuestion", question.toString())
        outState.putCharSequence("savedAnswer", answer.toString())
    }

    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
        super.onRestoreInstanceState(savedInstanceState)
        Log.i("Restored Instance State", "onRestoreInstanceState")

        val question = savedInstanceState.getCharSequence("savedQuestion")
        val answer = savedInstanceState.getCharSequence("savedAnswer")

        val txt = findViewById<EditText>(R.id.question)
        val txt2 = findViewById<EditText>(R.id.answer)

        txt.setText(question)
        txt2.setText(answer)
    }
}

标签： androidkotlin

解决方案

这不是onSaveInstanceStateand的用例onRestoreInstanceState。您应该在重新创建 Activity 时使用它们。例如：设备旋转。

在您的情况下，您正在启动一个新实例，SecondActivity当您从MainActivity.

要实现您想要的，您应该将问题和答案从MainActivity使用SecondActivitya传递Bundle，然后让用户编辑它们。

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