如何解决尝试使用 onSaveInstanceState 和 onRestoreSaveInstanceState 来保存我的活动状态,但它不起作用
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,它会将他们带到一个页面,在那里他们输入问题和答案,然后他们可以保存并返回到上一页,其中有一个新的创建文本设置为问题的按钮。除了在用户想要编辑问题/答案活动状态时我可以保存它的部分之外,我已经完成了所有这些编码和工作。我尝试使用 onSaveInstanceState 和 onRestoreSaveInstanceState 但它根本没有保存活动。有人能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)
}
}
解决方法
这不是 onSaveInstanceState
和 onRestoreInstanceState
的用例。您应该在重新创建 Activity 时使用它们。例如:设备旋转。
就您而言,当您从 SecondActivity
启动时,您正在启动 MainActivity
的新实例。
要实现您想要的效果,您应该使用 MainActivity
将问题和答案从 SecondActivity
传递到 Bundle
,然后让用户对其进行编辑。
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