我的记事本之-SQLite数据库的使用

先上两张应用截图

编辑界面

删除一条记录时

此应用共包括2个activity 主界面列表显示所有便笺的MainActivity和添加一条便笺的编辑界面SecondActivity

MainActivity

主要使用一个listView显示数据库中所有便笺 并添加点击条目编辑 长按条目删除

代码如下

public class MainActivity extends AppCompatActivity {
    private Button button;
    private ListView listView;
    private MyDataBase myDataBase;
    private LayoutInflater layoutInflater;
    private ArrayList<Note> arrayList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.listView1);
        layoutInflater = getLayoutInflater();
        myDataBase = new MyDataBase(this);
        button = (Button) findViewById(R.id.button1);
        arrayList = myDataBase.getArray();
        MyAdapter myAdapter = new MyAdapter(layoutInflater,arrayList);
        listView.setAdapter(myAdapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView,View view,int i,long l) {
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                intent.putExtra("id",arrayList.get(i).getId());
                startActivity(intent);
                MainActivity.this.finish();
            }
        });
        /** * 参数 　　parent 发生点击事件的 AbsListView。 　　view AbsListView 中被点击的视图。 　　position 视图在一览中的位置（索引）。 　　id 被点击条目的行 ID。 　　返回值 　　如果回调函数处理了长按事件，返回真；否则返回假。 */
        listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> adapterView,final int position,long l) {
                new AlertDialog.Builder(MainActivity.this).setTitle("删除").setMessage("数据无价，谨慎操作!")
                        .setNegativeButton("关闭",new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialogInterface,int i) {
                            }
                        }).setPositiveButton("删除",new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface,int i) {

                        myDataBase.deleteNote(arrayList.get(position).getId());
                        arrayList = myDataBase.getArray();
                        MyAdapter myAdapter = new MyAdapter(layoutInflater,arrayList);
                        listView.setAdapter(myAdapter);
                    }
                }).create().show();
                return true;
            }
        });
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                startActivity(intent);
                MainActivity.this.finish();

            }
        });
     }
  ###SecondActivity   实现新建和编辑一条便笺的功能
  和主界面通过Intent进行交互  并保存到数据库中
  代码如下

public class SecondActivity extends Activity{
Button save;
TextView textView1; //标题
TextView textView2; //内容
EditText title;
EditText content;
MyDataBase myDataBase;
Note note2; //第二个activity里面的note
int id;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_second);
    save=(Button)findViewById(R.id.save);
    textView1=(TextView)findViewById(R.id.t1);
    textView2=(TextView)findViewById(R.id.t2);
    title=(EditText)findViewById(R.id.title2);
    content=(EditText)findViewById(R.id.content2);
    myDataBase=new MyDataBase(this);
    id=getIntent().getIntExtra("id",0);
    if(id!=0){
        note2=myDataBase.getTitleandContent(id);
        title.setText(note2.getTitle());
        content.setText(note2.getContent());

    }
    save.setOnClickListener(new View.OnClickListener() {
                                @Override
                                public void onClick(View view) {
                                    isSave();
                                }
                            }
    );

}
@RequiresApi(api = Build.VERSION_CODES.N)
@Override
public void onBackPressed() {
   /* SimpleDateFormat simpleDateFormat= new SimpleDateFormat("yyyy.MM.dd  HH:mm:ss");
     */Date currentDate=new Date(System.currentTimeMillis());//获取当前时间

    String time=currentDate.toLocaleString();
            //simpleDateFormat.format(currentDate);
    String titles=title.getText().toString();
    String contents=content.getText().toString();
    //修改数据
    if (id != 0) {
        note2 = new Note( id,titles,contents,time);
        myDataBase.toUpdate(note2);
        Intent intent = new Intent(SecondActivity.this,MainActivity.class);
        startActivity(intent);
        SecondActivity.this.finish();
    }
    //新建文本
    else {
        note2 = new Note(titles,time);
        myDataBase.toInsert(note2);
        Intent intent = new Intent(SecondActivity.this,MainActivity.class);
        startActivity(intent);
        SecondActivity.this.finish();

    }
}
private void isSave(){
    java.text.SimpleDateFormat formatter   =   new java.text.SimpleDateFormat("yyyy.MM.dd  HH:mm:ss");
    Date   curDate   =   new   Date(System.currentTimeMillis());//获取当前系统时间
    String times   =   formatter.format(curDate);
    String titles=title.getText().toString();
    String contents=content.getText().toString();
    //修改数据
    if (id!=0) {
        note2 = new Note(id,times);
        myDataBase.toUpdate(note2);
        Intent intent = new Intent(SecondActivity.this,MainActivity.class);
        startActivity(intent);
        SecondActivity.this.finish();
    }
    //新建一条便笺
    else {
        if(titles!=null||contents!=null){
            note2 = new Note(titles,times);
            myDataBase.toInsert(note2);
        }

        Intent intent = new Intent(SecondActivity.this,MainActivity.class);
        startActivity(intent);
        SecondActivity.this.finish();

    }
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main,menu);
    return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // TODO Auto-generated method stub
    switch (item.getItemId()) {
        case R.id.action_settings:
            Intent intent = new Intent(Intent.ACTION_SEND);
            intent.setType("text/plain");
            intent.putExtra(Intent.EXTRA_TEXT,"标题" + title.getText().toString() + "内容" + content.getText().toString());
            startActivity(intent);
            break;

        default:
            break;
    }
    return false;
}

}

###数据库部分
  MyDataBase  主要实现数据库的添加删除 修改 通过android提供的SQLiteOpenHelper的自定义的子类MyDatabaseHelper实现对数据库的操作
  MyDataBase代码

public class MyDataBase {
Context context;
SQLiteDatabase sqLiteDatabase;
MyDatabaseHelper myDatabaseHelper;
public MyDataBase(Context context){
this.context=context;
myDatabaseHelper=new MyDatabaseHelper(context);
}
public ArrayList getArray(){
ArrayList arrayList=new ArrayList();
ArrayList arrayList1=new ArrayList();
sqLiteDatabase=myDatabaseHelper.getWritableDatabase();
//rawQuery()方法的第一个参数为select语句；
// 第二个参数为select语句中占位符参数的值，
// 如果select语句没有使用占位符，该参数可以设置为null。
Cursor cursor=sqLiteDatabase.rawQuery(“select id,title,date from note”,null);

cursor.moveToFirst();
    while (!cursor.isAfterLast()){
        int id=cursor.getInt(cursor.getColumnIndex("id"));
        String title=cursor.getString(cursor.getColumnIndex("title"));
        String date=cursor.getString(cursor.getColumnIndex("date"));
        Note note=new Note(id,date);
        arrayList.add(note);
        cursor.moveToNext();

    }cursor.close();
    sqLiteDatabase.close();
    for(int i=arrayList.size();i>0;i--){
        arrayList1.add(arrayList.get(i-1));
    }
    return arrayList1;
    //return  arrayList;
}
//第二个activity用到的  标题+内容
public Note getTitleandContent( int id){
    sqLiteDatabase=myDatabaseHelper.getWritableDatabase();
    Cursor cursor=sqLiteDatabase.rawQuery("select title,content from note where id='"+id+"'",null);
    cursor.moveToFirst();
    String title=cursor.getString(cursor.getColumnIndex("title"));
    String content =cursor.getString(cursor.getColumnIndex("content"));
    Note note=new Note(title,content);
    cursor.close();
    return note;
}

//execSQL(String sql,Object[] bindArgs)方法的第一个参数为SQL语句，
// 第二个参数为SQL语句中占位符参数的值，参数值在数组中的顺序要和占位符的位置对应。
// 修改数据
public void toUpdate(Note note){
    sqLiteDatabase =myDatabaseHelper.getWritableDatabase();
    sqLiteDatabase.execSQL("update note set title='"+ note.getTitle()+"',date='"+note.getDate()+"',content='"+note.getContent() +"' where id='"+ note.getId()+"'");
    sqLiteDatabase.close();

}
//插入数据,新建一条便笺
public void toInsert(Note note){
    sqLiteDatabase=myDatabaseHelper.getWritableDatabase();
    sqLiteDatabase.execSQL("insert into note(title,content,date) values('"+ note.getTitle()+"','"+note.getContent()+"','"+note.getDate()+"')");
    sqLiteDatabase.close();
}
//删除一条数据
public void deleteNote(int id){
    sqLiteDatabase=myDatabaseHelper.getWritableDatabase();
    sqLiteDatabase.execSQL("delete  from note where id=" + id+ "" );
    sqLiteDatabase.close();
}

}

MyDatabaseHelper代码如下:

public class MyDatabaseHelper extends SQLiteOpenHelper {
private Context context;
public static final String CREATE_NOTE=”create table if not exists note (id integer primary key autoincrement,title text,content text,date text)”;
public MyDatabaseHelper(Context context) {
super(context,“note”,null,1);
this.context=context;
}

@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
    sqLiteDatabase.execSQL(CREATE_NOTE);

}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase,int i,int j) {

}

}

###下面是一些实体和工具类
Note`public class Note {
    private String title;
    private String content;
    private int id;
    private String date;
    public  Note(int id,String title,String content,String date){
        this.content=content;
        this.title=title;
        this.date=date;
        this.id=id;
    }
    public Note(int id,String date){
        this.date=date;
        this.title=title;
        this.id=id;
    }
    public  Note(String title,String content){
        this.title=title;
        this.content=content;
    }

    public Note(String title,String date) {
        this.title=title;
        this.date=date;
        this.content=content;

    }

    public String getTitle(){
        return title;
            }
    public String getContent(){
        return content;
    }
    public int getId(){
        return id;
    }
    public String getDate(){
        return date;
    }
    }
adapter以及优化listView的viewHolder

public class MyAdapter extends BaseAdapter {
LayoutInflater layoutInflater;
ArrayList arrayList;
public MyAdapter(LayoutInflater layoutInflater,ArrayList arrayList){
this.arrayList=arrayList;
this.layoutInflater=layoutInflater;
}
@Override
public int getCount() {
return arrayList.size();
}

@Override
public Object getItem(int i) {
    return arrayList.get(i);
}

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

@Override
public View getView(int i,ViewGroup viewGroup) {
    ViewHolder viewHolder=new ViewHolder();
    if(view==null){
        view=layoutInflater.inflate(R.layout.adapter_listview,null);
        viewHolder.textView1=(TextView)view.findViewById(R.id.textview1);
        viewHolder.textView2=(TextView)view.findViewById(R.id.textview2);
        view.setTag(viewHolder);
    }
    viewHolder=(ViewHolder)view.getTag();
    viewHolder.textView1.setText(arrayList.get(i).getTitle());
    viewHolder.textView2.setText(arrayList.get(i).getDate());
    return view;
}

}
public class ViewHolder {
TextView textView1;
TextView textView2;
}
“`

总结 这个记事本app就是为了联系一下对于sqlite数据库的使用 很简单 但是真的收获很多
点击查看源码

（编辑：李大同）

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