用android studio实现简单的日记本详细代码，可增加日记到Dairy数据库中并且能用查看所有记录显示在listview中

以下是一个简单的日记本应用的代码，使用Android Studio和SQLite数据库来实现：

activity_main.xml布局文件：

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

    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="输入你的日记"
        android:gravity="top"
        android:padding="10dp"/>

    <Button
        android:id="@+id/buttonSave"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="保存"/>

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

Dairy.java数据模型类：

public class Dairy {
    private int id;
    private String text;
    private String date;

    public Dairy() {}

    public Dairy(int id, String text, String date) {
        this.id = id;
        this.text = text;
        this.date = date;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }
}

DairyAdapter.java适配器类：

public class DairyAdapter extends BaseAdapter {
    private Context context;
    private List<Dairy> dairyList;

    public DairyAdapter(Context context, List<Dairy> dairyList) {
        this.context = context;
        this.dairyList = dairyList;
    }

    @Override
    public int getCount() {
        return dairyList.size();
    }

    @Override
    public Object getItem(int position) {
        return dairyList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_dairy, null);
        TextView textViewText = view.findViewById(R.id.textViewText);
        TextView textViewDate = view.findViewById(R.id.textViewDate);
        Dairy dairy = dairyList.get(position);
        textViewText.setText(dairy.getText());
        textViewDate.setText(dairy.getDate());
        return view;
    }
}

item_dairy.xml布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="10dp">

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

    <TextView
        android:id="@+id/textViewDate"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        android:textColor="#666666"/>

</LinearLayout>

MainActivity.java主活动类：

public class MainActivity extends AppCompatActivity {
    private EditText editText;
    private Button buttonSave;
    private ListView listView;
    private List<Dairy> dairyList = new ArrayList<>();
    private DairyAdapter dairyAdapter;
    private SQLiteDatabase sqLiteDatabase;

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

        editText = findViewById(R.id.editText);
        buttonSave = findViewById(R.id.buttonSave);
        listView = findViewById(R.id.listView);
        dairyAdapter = new DairyAdapter(this, dairyList);
        listView.setAdapter(dairyAdapter);

        buttonSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String text = editText.getText().toString();
                if (!TextUtils.isEmpty(text)) {
                    insertDairy(text);
                    editText.setText("");
                    queryAllDairy();
                }
            }
        });

        sqLiteDatabase = openOrCreateDatabase("Dairy.db", Context.MODE_PRIVATE, null);
        sqLiteDatabase.execSQL("CREATE TABLE IF NOT EXISTS Dairy (id INTEGER PRIMARY KEY AUTOINCREMENT, text TEXT, date TEXT)");
        queryAllDairy();
    }

    private void insertDairy(String text) {
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String date = df.format(new Date());
        sqLiteDatabase.execSQL("INSERT INTO Dairy (text, date) VALUES (?, ?)", new Object[]{text, date});
    }

    private void queryAllDairy() {
        dairyList.clear();
        Cursor cursor = sqLiteDatabase.rawQuery("SELECT * FROM Dairy ORDER BY date DESC", null);
        while (cursor.moveToNext()) {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String text = cursor.getString(cursor.getColumnIndex("text"));
            String date = cursor.getString(cursor.getColumnIndex("date"));
            Dairy dairy = new Dairy(id, text, date);
            dairyList.add(dairy);
        }
        dairyAdapter.notifyDataSetChanged();
        cursor.close();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        sqLiteDatabase.close();
    }
}

以上代码实现了一个简单的日记本应用，主要通过SQLite数据库存储日记信息，并使用ListView显示所有的日记记录。代码中包含了数据模型类、适配器类、布局文件和主活动类等。其中主要的实现逻辑是：在点击“保存”按钮时将日记内容插入到数据库中，然后重新查询出所有的日记记录并更新ListView显示。