Android小项目--简易记事本的实现

淡淡的烟草味﹌ 2022-03-29 12:10 249阅读 0赞

下面实现了一个简易的记事本，效果如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2F5YW5nYW5uOTE1_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2F5YW5nYW5uOTE1_size_16_color_FFFFFF_t_70 1]  
主要使用数据库存储数据。  
完整代码链接：  
[https://download.csdn.net/download/ayangann915/10904192][https_download.csdn.net_download_ayangann915_10904192]

下面是部分代码：  
**MainActivity:**

public class MainActivity extends AppCompatActivity implements View.OnClickListener { 
    
        private EditText subject;
        private EditText body;
        private EditText date;
        private Button chooseDate;
        private Button add;
        private Button query;
        private ListView result;
        private LinearLayout title;
        private MyDataBaseHelper mMyDataBaseHelper;
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            initView();
        }
    
        private void initView() { 
            //控件初始化
            subject=(EditText)findViewById(R.id.subject);
            body=(EditText)findViewById(R.id.body);
            date=(EditText)findViewById(R.id.date);
            chooseDate=(Button)findViewById(R.id.chooseDate);
            add=(Button)findViewById(R.id.add);
            query=(Button)findViewById(R.id.query);
            result=(ListView)findViewById(R.id.result);
            title=(LinearLayout)findViewById(R.id.title);
    
            //选择日期，添加，查询的监听事件
            chooseDate.setOnClickListener(this);
            add.setOnClickListener(this);
            query.setOnClickListener(this);
            //查询情况默认隐藏，只有点击查询时才有效果
            title.setVisibility(View.INVISIBLE);
        }
    
        @Override
        public void onClick(View v) { 
            //创建数据库
            mMyDataBaseHelper=new MyDataBaseHelper(MainActivity.this,"memento.db",null,1);
            SQLiteDatabase sqLiteDatabase=mMyDataBaseHelper.getReadableDatabase();
            //获取输入框的内容
            String strSubject=subject.getText().toString().trim();
            String strBody=body.getText().toString().trim();
            String strDate=date.getText().toString().trim();
    
            switch (v.getId()){ 
                case R.id.chooseDate:
                    Calendar calendar=Calendar.getInstance();
                    //选择时间，并将时间设置在date中
                    new DatePickerDialog(MainActivity.this, new DatePickerDialog.OnDateSetListener() { 
                        @Override
                        public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) { 
                            date.setText(year+"-"+month+"-"+dayOfMonth);
                        }
                    },calendar.get(Calendar.YEAR),calendar.get(Calendar.MONTH),calendar.get(Calendar.DAY_OF_MONTH)).show();
                    break;
                case R.id.add:
                    //添加内容到数据库中，添加方法是add
                    title.setVisibility(View.INVISIBLE);
                    add(sqLiteDatabase,strSubject,strBody,strDate);
                    Toast.makeText(this, "success!", Toast.LENGTH_SHORT).show();
                    result.setAdapter(null);
                    break;
                case R.id.query:
                    //查询时显示结果设置为visible
                    title.setVisibility(View.VISIBLE);
                    //查询的结果保存在cursor中
                    Cursor cursor=query(sqLiteDatabase,strSubject,strBody,strDate);
                    SimpleCursorAdapter simpleCursorAdapter=new SimpleCursorAdapter(MainActivity.this,R.layout.result,cursor,new String[]{ "_id", "subject", "body", "date"},
                            new int[]{ R.id.memento_num, R.id.memento_subject, R.id.memento_body, R.id.memento_date});
                    //为listview添加适配器
                    result.setAdapter(simpleCursorAdapter);
                    break;
            }
        }
    
        //添加数据到数据库中的方法
        public void add(SQLiteDatabase sqLiteDatabase,String subject,String body,String date){ 
            sqLiteDatabase.execSQL("Insert into memento_tb values(null,?,?,?)",new String[]{ subject,body,date});
            //初始设置为空
            this.subject.setText("");
            this.body.setText("");
            this.date.setText("");
        }
    
        //查询的方法，返回值为cursor
        public Cursor query(SQLiteDatabase sqLiteDatabase, String subject, String body, String date){ 
            Cursor cursor = sqLiteDatabase.rawQuery(
                    "select * from memento_tb where subject like ? and body like ? and date like ? ",
                    new String[]{ "%" + subject + "%", "%" + body + "%",
                            "%" + date + "%"});//对表的查询（insert的操作）
            return cursor;
        }
    
        protected void onDestroy() { 
            super.onDestroy();
            if (mMyDataBaseHelper != null) { 
                mMyDataBaseHelper.close();
            }
        }
    }

**MyDataBaseHelper：**

public class MyDataBaseHelper extends SQLiteOpenHelper { 
        //创建数据库的语句
        final String CREATE_TABLE_SQL =
                "create table memento_tb(_id integer primary " +
                        "key autoincrement,subject,body,date)";     //建表
    
    
        public MyDataBaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) { 
            super(context, name, factory, version);
        }
    
        //执行建表的操作
        @Override
        public void onCreate(SQLiteDatabase db) { 
            db.execSQL(CREATE_TABLE_SQL);
        }
    
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
            System.out.println("---------" + oldVersion + "------->" + newVersion);
        }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2F5YW5nYW5uOTE1_size_16_color_FFFFFF_t_70]: /images/20220329/d5abad85a8364255bacd8bae465a688a.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2F5YW5nYW5uOTE1_size_16_color_FFFFFF_t_70 1]: /images/20220329/ac9c8fbcd3864e508c741dae46b8147a.png
[https_download.csdn.net_download_ayangann915_10904192]: https://download.csdn.net/download/ayangann915/10904192