錯(cuò)誤發(fā)生在 setAdapter 行上。我找不到錯(cuò)誤在哪里。它與空異常無(wú)關(guān)。有些事情不正常java.lang.RuntimeException：無(wú)法啟動(dòng)活動(dòng) ComponentInfo{com.example.myapplication/com.example.myapplication.Namelist}：java.lang.NullPointerException：嘗試調(diào)用虛擬方法 'void android.widget.ListView.setAdapter(android. widget.ListAdapter)' 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913) 處的 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 處的空對(duì)象引用上 android.app.servertransaction.LaunchActivityItem.execute （LaunchActivityItem.java:78）位于主要類(lèi)別：public class Namelist extends AppCompatActivity {String[] mobileArray = {"Android","IPhone","WindowsMobile","Blackberry",        "WebOS","Ubuntu","Windows7","Max OS X"};ListView l1;ArrayAdapter<String> arrayAdapter;@Overrideprotected void onCreate(Bundle savedInstanceState) {    l1 = (ListView) findViewById(R.id.list);    arrayAdapter = new ArrayAdapter<String>(Namelist.this,R.layout.activity_namelist,mobileArray);   l1.setAdapter(arrayAdapter);    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_namelist);}}活動(dòng)XML：<?xml version="1.0" encoding="utf-8"?><androidx.constraintlayout.widget.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:layout_width="match_parent"android:layout_height="match_parent"tools:context=".Namelist"><ListView    android:id="@+id/list"    android:layout_width="409dp"    android:layout_height="729dp"    app:layout_constraintBottom_toBottomOf="parent"    app:layout_constraintEnd_toEndOf="parent"    app:layout_constraintStart_toStartOf="parent"    app:layout_constraintTop_toTopOf="parent" /></androidx.constraintlayout.widget.ConstraintLayout>提前致謝