找不到类符号--Android Studio

Question

I have just started building an android app following this tutorial. Everything went fine till the last step where we are making an Intent object to bring up the NoteSelect activity, despite the class being in the same folder. Here is the error -

Information:Gradle tasks [:app:assembleDebug]
F:\Path\Memos\app\src\main\java\com\example\memos\memos\MainActivity.java
Error:(99, 57) error: cannot find symbol class NoteSelect
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.
Information:BUILD FAILED in 19s
Information:2 errors
Information:0 warnings
Information:See complete output in console

Here is the hierarchy -

MainActivity.java (onOptionsItemSelected())

package com.example.memos.memos;

@Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        Intent myIntent = new Intent(MainActivity.this, NoteSelect.class);
        if (id == R.id.action_settings) {
            startActivity(myIntent);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

NoteSelect.java (didn't mention trivial imports)

import com.example.memos.memos.R;

public class NoteSelect extends AppCompatActivity {

    private List <NotesBuilder> notesList = new ArrayList<>();
    private NotesAdapter nAdapter;
    private RecyclerView notesRecycler;

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

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        notesRecycler = findViewById(R.id.notes);

        nAdapter = new NotesAdapter(notesList);
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        notesRecycler.setLayoutManager(mLayoutManager);
        notesRecycler.setItemAnimator(new DefaultItemAnimator());
        notesRecycler.setAdapter(nAdapter);

        prepareNotes();

    }

    private void prepareNotes() {
        File directory;
        directory = getFilesDir();
        File[] files = directory.listFiles();
        String theFile;
        for (int f = 1; f <= files.length; f++) {
            theFile = "Note" + f + ".txt";
            NotesBuilder note = new NotesBuilder(theFile, Open(theFile));
            notesList.add(note);
        }

    }

    public String Open(String fileName) {
        String content = "";
        try {
            InputStream in = openFileInput(fileName);
            if ( in != null) {
                InputStreamReader tmp = new InputStreamReader( in );
                BufferedReader reader = new BufferedReader(tmp);
                String str;
                StringBuilder buf = new StringBuilder();
                while ((str = reader.readLine()) != null) {
                    buf.append(str + "\n");
                } in .close();

                content = buf.toString();
            }
        } catch (java.io.FileNotFoundException e) {} catch (Throwable t) {
            Toast.makeText(this, "Exception: " + t.toString(), Toast.LENGTH_LONG).show();
        }

        return content;
    }
}

Issue seems to be there with AndroidManifest.xml , content_note_select.xml and activity_note_select.xml .

So far I have tried including NoteSelect.java in the same package as MainActivity.java that resolves the NoteSelect class not found issue but further leads to NoteBuilder and NoteAdapter class not found the issue in NoteSelect.java . Moreover, since nothing like this has been mentioned in the original tutorial I don't prefer it anyway.

Any ideas where I am going wrong?

Answer 1

So far I have tried including NoteSelect.java in the same package as MainActivity.java that resolves the NoteSelect class not found the issue but further leads to NoteBuilder and NoteAdapter class not found

Well, that was correct, but you also need to move the other classes instead of leaving them in src/main/java folder

Java cannot resolve classes "above" the current package.

Try this layout

com.example.memos/
    MainActivity.java
    notes/
        NoteSelectionActivity.java   <--- It's an activity, so rename your class to this
        NotesAdapter.java
        Note.java  <---- A POJO class. // There's no reason to name it "Builder" when it isn't using a "Builder Pattern"

Then in the MainActivity

package com.example.memos;

import com.example.memos.notes.NoteSelectionActivity;

And in the NoteSelectionActivity

package com.example.memos.notes;

// No imports needed for classes in the same package