CRASH问题：java.lang.NullPointerException

java.lang.NullPointerException: Attempt to invoke virtual method ‘void android.widget.ImageView.setImageResource(int)’ on a null object reference

今天在家练习ListView的时候，遇到一个java.lang.NullPointerException的空指针异常，log如下：

2020-05-10 15:40:29.249 20436-20436/? E/k.myapplicatio: Unknown bits set in runtime_flags: 0x8000
2020-05-10 15:40:29.602 20436-20436/com.hpeak.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.hpeak.myapplication, PID: 20436
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference
        at com.hpeak.myapplication.MainActivity$MyAdapter.getView(MainActivity.java:72)
        at android.widget.AbsListView.obtainView(AbsListView.java:2437)
        at android.widget.ListView.measureHeightOfChildren(ListView.java:1423)
        at android.widget.ListView.onMeasure(ListView.java:1329)
        at android.view.View.measure(View.java:25253)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6891)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1204)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:723)
        at android.view.View.measure(View.java:25253)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6891)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.view.View.measure(View.java:25253)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6891)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
        at android.view.View.measure(View.java:25253)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6891)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at com.android.internal.policy.DecorView.onMeasure(DecorView.java:851)
        at android.view.View.measure(View.java:25253)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:3419)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:2124)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2426)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:2008)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8600)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1036)
        at android.view.Choreographer.doCallbacks(Choreographer.java:859)
        at android.view.Choreographer.doFrame(Choreographer.java:794)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1021)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:247)
        at android.app.ActivityThread.main(ActivityThread.java:8263)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:511)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:942)

根据log信息依次定位到下图所示代码处：


暂时看代码并没有看出有什么问题，然后又看了一遍代码，加了log，将imgResIds[position]打印出来，发现打印不出来内容，又发现setImageResource(imgResIds[position])是由imageView调用的，仔细分析了一下imageView的来源，终于发现是imageView的问题，故解决方法是：
将代码

//            1.解析布局文件，成为view
            LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
            View view = inflater.inflate(R.layout.list_item, parent, false);
//            2.填充当前项的数据
            ImageView imageView = findViewById(R.id.img1);
            imageView.setImageResource(imgResIds[position]);
            
            TextView textView = view.findViewById(R.id.text1);
            textView.setText(names[position]);

修改为

//            1.解析布局文件，成为view
            LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
            View view = inflater.inflate(R.layout.list_item, parent, false);
//            2.填充当前项的数据
            ImageView imageView = view.findViewById(R.id.img1);
            imageView.setImageResource(imgResIds[position]);

            TextView textView = view.findViewById(R.id.text1);
            textView.setText(names[position]);

再次运行，正常。运行结果如下图所示：

至此，问题解决。