com.example.autocompleteex.MainActivity.onCreate（MainActivity.java:33）上的NullPointerException

爪哇

包com.example.autocompleteex;

导入androidx.appcompat.app.AppCompatActivity;

导入android.content.Intent;导入android.os.Bundle;导入android.view.View;导入android.widget.Adapter;导入android.widget.AdapterView;导入android.widget.ArrayAdapter;导入android.widget.AutoCompleteTextView;导入android.widget.Button;

公共类MainActivity扩展了AppCompatActivity {

AutoCompleteTextView tv;
Button b;
String da;
String name[]={"aa","ab","abc","hj","hyk","rty","rik","rkl"};
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    tv=findViewById(R.id.autoCompleteTextView);
    b=findViewById(R.id.button);
    ArrayAdapter<String>arr=new ArrayAdapter<>(MainActivity.this,R.layout.support_simple_spinner_dropdown_item,name);
    tv.setAdapter(arr);
   tv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
       @Override
       public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
           da = (String)parent.getItemAtPosition(position);
       }
   });
    b.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent obj  = new Intent(MainActivity.this,Selected.class);
            obj.putExtra("k",da);
            startActivity(obj);
        }
    });
} }