Android Studio完成记事本案例

为了完成记事本案例，我们需要进行以下步骤：

1.创建一个实体类Note，用于存放每个记录的内容和时间属性。

public class Note {
    private String content;
    private String time;

    public Note() {}

    public Note(String content, String time) {
        this.content = content;
        this.time = time;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }
}

2.创建一个用于显示记录列表的布局文件note_item.xml。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/tv_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="18sp" />

    <TextView
        android:id="@+id/tv_time"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:textColor="@android:color/darker_gray" />

</LinearLayout>

3.创建一个用于添加新记录的布局文件activity_add_note.xml。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <EditText
        android:id="@+id/et_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="输入记录内容" />

    <Button
        android:id="@+id/btn_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="添加" />

</LinearLayout>

4.创建一个用于显示记录列表的Activity类MainActivity。

public class MainActivity extends AppCompatActivity {

    private List<Note> noteList = new ArrayList<>();
    private RecyclerView recyclerView;
    private NoteAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = findViewById(R.id.recycler_view);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        adapter = new NoteAdapter(noteList);
        recyclerView.setAdapter(adapter);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this, AddNoteActivity.class);
                startActivityForResult(intent, 1);
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 1 && resultCode == RESULT_OK) {
            String content = data.getStringExtra("content");
            String time = data.getStringExtra("time");
            Note note = new Note(content, time);
            noteList.add(note);
            adapter.notifyItemInserted(noteList.size() - 1);
        }
    }

    private class NoteAdapter extends RecyclerView.Adapter<NoteAdapter.ViewHolder> {

        private List<Note> noteList;

        private NoteAdapter(List<Note> noteList) {
            this.noteList = noteList;
        }

        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.note_item, parent, false);
            final ViewHolder holder = new ViewHolder(view);
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    int position = holder.getAdapterPosition();
                    Note note = noteList.get(position);
                    Toast.makeText(MainActivity.this, note.getContent(), Toast.LENGTH_SHORT).show();
                }
            });
            return holder;
        }

        @Override
        public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
            Note note = noteList.get(position);
            holder.tvContent.setText(note.getContent());
            holder.tvTime.setText(note.getTime());
        }

        @Override
        public int getItemCount() {
            return noteList.size();
        }

        private class ViewHolder extends RecyclerView.ViewHolder {

            private TextView tvContent;
            private TextView tvTime;

            private ViewHolder(@NonNull View itemView) {
                super(itemView);
                tvContent = itemView.findViewById(R.id.tv_content);
                tvTime = itemView.findViewById(R.id.tv_time);
            }
        }
    }
}

5.创建一个用于添加新记录的Activity类AddNoteActivity。

public class AddNoteActivity extends AppCompatActivity {

    private EditText etContent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_note);

        etContent = findViewById(R.id.et_content);

        Button btnAdd = findViewById(R.id.btn_add);
        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String content = etContent.getText().toString();
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
                String time = sdf.format(new Date());
                Intent intent = new Intent();
                intent.putExtra("content", content);
                intent.putExtra("time", time);
                setResult(RESULT_OK, intent);
                finish();
            }
        });
    }
}

以上就是Android Studio完成记事本案例的步骤。如果您需要更详细的代码实现，请参考相关的Android开发教程。