[英]Can anyone help me about I am getting error code 400 while working with AsyncTask in Android
[英]can anyone help me out why I am getting null value even there is no error in the code
package com.example.myquizapp
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.ProgressBar
import android.widget.TextView
這是我的代碼
class QuizActivity : AppCompatActivity() {
private var progressBar : ProgressBar?= null
private var tvProgress : TextView? = null
override fun onCreate(savedInstanceState: Bundle?) {
progressBar = findViewById(R.id.progressBar)
在 hover R.id.progressBar 我得到:public static final int progressBar = 1000004
tvProgress = findViewById(R.id.tv_progress)
// public static final int tv_progress = 100000
//在 hover progressBar 上我得到:private final var progressBar: ProgressBar?
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_quiz)
var currentPosition = 1
progressBar?.progress=currentPosition
tvProgress?.text="${currentPosition}/${progressBar?.max}"
Log.e("currentPosition" "${currentPosition}) // 1
Log.e("ProgressBar", "${progressBar}") // null, getting null value on logcat
Log.e("TvOrogress", "${tvProgress}")// null, getting null value on logcat
Log.e("tvProgress",${tvProgress?.text.toString} // null
}
}
在setContentView()
之后移動findViewById()
調用。
setContentView()
膨脹視圖層次結構並將其添加到活動中。 findViewById()
在活動視圖層次結構中查找視圖,並且在setContentView()
之前為空,因此findViewById()
返回 null。
將 findViewById() 移至 onViewCreated 方法
override fun onViewCreated(savedInstanceState: Bundle?) {
progressBar = findViewById(R.id.progressBar)
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