Android Studio报错
1.

2020-04-10 00:21:36.686 1927-1927/? E/netmgr: Failed to open QEMU pipe 'qemud:network': Invalid argument
2020-04-10 00:21:36.686 1927-1927/? E/netmgr: WifiForwarder unable to open QEMU pipe: Invalid argument
2020-04-10 00:21:39.528 2000-2026/system_process E/memtrack: Couldn't load memtrack module
2020-04-10 00:21:40.479 2000-2026/system_process E/memtrack: Couldn't load memtrack module

解决办法

<application
    ..
    android:usesCleartextTraffic="true"
    >

 Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.query on null object reference

解决方法

db = getWritableDatabase();
Cursor c = db.query(...);

android - Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

Null pointer try to say that the textview is null. That can happen beacause the findviewbyid is not matching with the right one on your xml. Be sure your id matches on your xml and java file

TextView txtName = (TextView)findViewById(R.id.nameText);

txtName 和nameText不能相同