Question

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

EditText myeditText1;
EditText myeditText2;
Button myButton;

Double myfirstET1;
Double myfirstET2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    myeditText1 = (EditText) findViewById(R.id.editText1);
    myeditText2 = (EditText) findViewById(R.id.editText2);
    myButton = (Button) findViewById(R.id.buttonID);
    final TextView myTextView = (TextView) findViewById(R.id.textView2);


    myButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            myfirstET1 = Double.parseDouble(myeditText1.getText().toString());
            myfirstET2 = Double.parseDouble(myeditText2.getText().toString());
            final ListView mListView = (ListView) findViewById(R.id.mList);

            if ((myeditText1.getText().length() > 0) && (myeditText2.getText().length() > 0)) {
                double oper1 = Double.parseDouble(myeditText1.getText().toString());
                double oper2 = Double.parseDouble(myeditText2.getText().toString());
                double result = oper1 / oper2;
                myTextView.setText(Double.toString(result));


                Double myyList[] = {oper1, oper2 + 1, oper2 + 1};

                ListAdapter myAdapter = new ArrayAdapter<Double>(this, android.R.layout.simple_list_item_1, myyList);
                mListView.setAdapter(myAdapter);

            }

        }
    });

创建ListView并为其设置适配器后，我在ListAdapter中收到错误。如何修复它或者它是什么？我希望我用我编写的代码清楚我的moto。

所有建议都深受赞赏。

Answer 1

您需要在匿名类中使用MainActivity.this而不是this来将此实际的Activity上下文称为

 ListAdapter myAdapter = new ArrayAdapter<Double>(MainActivity.this, android.R.layout.simple_list_item_1, myyList);
 //                                             ^^^^^^^^^^^^^^^^^^

并提及类型并使用ArrayAdapter而非ListAdapter

 ArrayAdapter<Double> myAdapter = new ArrayAdapter<>(MainActivity.this...);
 //         ^^^^^^^

Answer 2

你应该使用这样的东西

ArrayAdapter<Double> myAdapter = new ArrayAdapter<Double>(this, android.R.layout.simple_list_item_1, myyList);

Answer 3

您可以使用

ListAdapter myAdapter = new ArrayAdapter<>(MainActivity.this, 
android.R.layout.simple_list_item_1, myyList);
mListView.setAdapter(myAdapter);

或

ListAdapter myAdapter = new ArrayAdapter<Double>(MainActivity.this, 
android.R.layout.simple_list_item_1, myyList);
                mListView.setAdapter(myAdapter);

但请确保使用MainActivity.this

而不是这个

无法解析ArrayAdapter中的构造函数

3 个答案: