当尝试setText（Android工作室）时出现空指针异常

Question

我一直有一个奇怪的问题，我尝试创建一个与我总是一样的textView，但现在当我初始化textView和setText时，我得到一个空指针例外，并不能找出我做错了什么。

@Override 
protected void onCreate(Bundle savedInstanceState) 
{ 
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_main); 

TextView test = (TextView) findViewById(R.id.randomID); 
test.setText("sample text"); 
} 

XML

<?xml version="1.0" encoding="utf-8"?> 
<android.support.constraint.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:app="http://schemas.android.com/apk/res-auto" 
xmlns:tools="http://schemas.android.com/tools" 
android:id="@+id/Constraint" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:fitsSystemWindows="true" 
tools:openDrawer="start"> 

<RelativeLayout 
    android:id="@+id/relativeLayout" 
    android:layout_width="364dp" 
    android:layout_height="223dp" 
    android:layout_marginBottom="8dp" 
    android:layout_marginEnd="8dp" 
    android:layout_marginLeft="8dp" 
    android:layout_marginRight="8dp" 
    android:layout_marginStart="8dp" 
    android:layout_marginTop="8dp" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toTopOf="@+id/cityID" 
    app:layout_constraintVertical_bias="0.006"> 

    <ImageView 
     android:id="@+id/weatherImage" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_marginBottom="16dp" 
     android:layout_marginEnd="16dp" 
     android:layout_marginLeft="16dp" 
     android:layout_marginRight="16dp" 
     android:layout_marginStart="16dp" 
     android:layout_marginTop="16dp" 
     app:layout_constraintBottom_toBottomOf="parent" 
     app:layout_constraintHorizontal_bias="0.0" 
     app:layout_constraintLeft_toLeftOf="parent" 
     app:layout_constraintRight_toLeftOf="@+id/celsius" 
     app:layout_constraintTop_toBottomOf="@+id/loadingLocation" 
     app:layout_constraintVertical_bias="0.555" 
     app:srcCompat="@drawable/thunder_cloud_rain"/> 
</RelativeLayout> 

<android.support.v7.widget.Toolbar 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/settingsToolbar" 
    android:titleTextColor="@color/white" 
    android:layout_width="0dp" 
    android:layout_height="wrap_content" 
    android:layout_marginBottom="8dp" 
    android:background="@color/colorPrimary" 
    android:minHeight="?android:attr/actionBarSize" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.0" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toTopOf="parent" 
    app:layout_constraintVertical_bias="0.0" 
    app:theme="@style/ToolBarStyle"/> 

<TextView 
    android:id="@+id/celsius" 
    android:layout_width="0dp" 
    android:layout_height="wrap_content" 
    android:layout_marginBottom="8dp" 
    android:layout_marginEnd="8dp" 
    android:layout_marginLeft="8dp" 
    android:layout_marginRight="8dp" 
    android:layout_marginStart="8dp" 
    android:layout_marginTop="8dp" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="45sp" 
    android:textStyle="bold" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.0" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/settingsToolbar" 
    app:layout_constraintVertical_bias="0.035" 
    tools:text="96"/> 

<TextView 
    android:id="@+id/skyForecast" 
    android:layout_width="0dp" 
    android:layout_height="wrap_content" 
    android:layout_marginBottom="7dp" 
    android:gravity="center" 
    android:includeFontPadding="false" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="14sp" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    tools:text="Scattered Clouds" 
    app:layout_constraintHorizontal_bias="1.0" 
    android:layout_marginTop="8dp" 
    app:layout_constraintTop_toBottomOf="@+id/celsius" 
    app:layout_constraintVertical_bias="0.0"/> 

<TextView 
    android:id="@+id/cityID" 

    android:layout_width="0dp" 
    android:layout_height="wrap_content" 
    android:layout_marginLeft="8dp" 
    android:layout_marginRight="8dp" 
    android:layout_marginTop="4dp" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="16sp" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.502" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/skyForecast" 
    app:layout_constraintVertical_bias="0.005" 
    tools:text="Redmond, Washington" 
    android:layout_marginStart="8dp" 
    android:layout_marginEnd="8dp"/> 

<TextView 
    android:id="@+id/currentTime" 

    android:layout_width="0dp" 
    android:layout_height="wrap_content" 
    android:layout_marginEnd="8dp" 
    android:layout_marginLeft="8dp" 
    android:layout_marginRight="8dp" 
    android:layout_marginStart="8dp" 
    android:layout_marginTop="4dp" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="16sp" 
    android:textStyle="bold" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.0" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/skyForecast" 
    app:layout_constraintVertical_bias="0.554" 
    tools:text="Monday, 10:30 am"/> 

<TextView 
    android:id="@+id/sunrise" 

    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_marginEnd="8dp" 
    android:layout_marginLeft="8dp" 
    android:layout_marginRight="8dp" 
    android:layout_marginStart="8dp" 
    android:layout_marginTop="4dp" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="18sp" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.057" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/skyForecast" 
    app:layout_constraintVertical_bias="0.854" 
    tools:text="6:30 am"/> 

<TextView 
    android:id="@+id/windSpeed" 

    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="18sp" 
    app:layout_constraintVertical_bias="0.856" 
    tools:text="10 m/s" 
    app:layout_constraintTop_toTopOf="@+id/sunrise" 
    tools:layout_editor_absoluteX="159dp"/> 

<TextView 
    android:id="@+id/randomID" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="18sp" 
    tools:text="10 m/s" 
    android:layout_marginTop="8dp" 
    app:layout_constraintTop_toBottomOf="@+id/currentTime" 
    app:layout_constraintBottom_toBottomOf="parent" 
    android:layout_marginBottom="8dp" 
    android:layout_marginRight="8dp" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintLeft_toRightOf="@+id/windSpeed" 
    android:layout_marginLeft="8dp" 
    app:layout_constraintHorizontal_bias="0.284" 
    app:layout_constraintVertical_bias="0.649"/> 

<TextView 
    android:id="@+id/sunset" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_marginEnd="8dp" 
    android:layout_marginLeft="8dp" 
    android:layout_marginRight="8dp" 
    android:layout_marginStart="8dp" 
    android:textAlignment="center" 
    android:textColor="@color/white" 
    android:textSize="18sp" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.059" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/sunrise" 
    app:layout_constraintVertical_bias="0.0" 
    tools:text="7:30 pm"/> 

<ProgressBar 
    android:id="@+id/loadingLocation" 
    style="?android:attr/progressBarStyle" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/settingsToolbar" 
    app:layout_constraintVertical_bias="0.438" 
    tools:visibility="visible" 
    android:layout_marginLeft="8dp" 
    app:layout_constraintLeft_toLeftOf="parent" 
    android:layout_marginRight="8dp" 
    app:layout_constraintRight_toRightOf="parent" 
    android:layout_marginStart="8dp" 
    android:layout_marginEnd="8dp"/> 

<View 
    android:id="@+id/view" 
    android:layout_width="wrap_content" 
    android:layout_height="1dp" 
    android:layout_marginBottom="8dp" 
    android:background="@color/colorPrimaryDark" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintHorizontal_bias="0.0" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/settingsToolbar" 
    app:layout_constraintVertical_bias="0.0"/> 

<ImageView 
    android:id="@+id/imageView" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_marginRight="8dp" 
    app:layout_constraintRight_toRightOf="parent" 
    app:srcCompat="@drawable/ic_wb_sunny_black_24dp" 
    android:layout_marginLeft="8dp" 
    app:layout_constraintLeft_toLeftOf="parent" 
    android:layout_marginTop="8dp" 
    app:layout_constraintTop_toBottomOf="@+id/currentTime" 
    app:layout_constraintBottom_toBottomOf="parent" 
    android:layout_marginBottom="8dp" 
    app:layout_constraintHorizontal_bias="0.107" 
    app:layout_constraintVertical_bias="0.397" 
    android:layout_marginStart="8dp" 
    android:layout_marginEnd="8dp"/> 

<ImageView 
    android:id="@+id/imageView2" 
    android:layout_width="28dp" 
    android:layout_height="28dp" 
    android:layout_marginBottom="8dp" 
    android:layout_marginTop="8dp" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintTop_toBottomOf="@+id/currentTime" 
    app:layout_constraintVertical_bias="0.375" 
    app:srcCompat="@drawable/wind_512" 
    tools:layout_editor_absoluteX="173dp"/> 

我试图重建项目，unistalling应用，清洁工程，建设APK，我非常困惑什么，我做错了。

Answer 1

感谢米哈伊尔，我发现了这个问题。事实证明，我有我的activity_main的v23 version，使其在其他版本的Android上工作，并使其在错误的activity_main。