Android 在不同activity控制同一个数据库

实现效果对MainActivity界面的edit写数据库中对应的age，如果查询到就跳转到Main2Activity界面否则不跳转，在Main2Activity布局上edit写对应age然后跳转到MainActivity，输入之前写的age如果没有跳转证明删除成功。

思路

建立一个封装类对SQLiteOpenHelper的继承类管理

直接上代码

1.创建的一个继承SQLiteOpenHelper的类 mybase

public class myBASE extends SQLiteOpenHelper {
private static final String my_table="create table mytable(" +
        "id integer primary key autoincrement," +
        "name text," +
        "age integer)";
private Context mContext;
public myBASE(Context context,String name,SQLiteDatabase.CursorFactory factory,int version){
    super(context,name,factory,version);
    mContext=context;
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(my_table);
    ContentValues values=new ContentValues();
    values.put("name","tony");
    values.put("age",16);
    db.insert("mytable",null,values);
    values.clear();
    values.put("name","jack");
    values.put("age",25);
    db.insert("mytable",null,values);
}

}

2.创建管理mybase的类

public class base {
private static final String table="mytable.db";
private static final int version=1;
private static base base=null;
private SQLiteOpenHelper myBASE;
private base(Context context){
    this.myBASE=new myBASE(context,table,null,version);
}
public static synchronized base setBase(Context context){
    if (base==null){
        base=new base(context);
    }
    return base;
}
public SQLiteOpenHelper getMyBASE(){
    return this.myBASE;
}
public SQLiteDatabase getWrite(){
    return myBASE.getWritableDatabase();
}

public SQLiteDatabase getread(){
    return myBASE.getReadableDatabase();
}

}

3.MainActivity代码 布局就不写了 就一个button 和一个edit

public class MainActivity extends AppCompatActivity  {
EditText text;
Button btn_start;
String string;
Cursor cursor;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btn_start=(Button)findViewById(R.id.btn_start);
    text=(EditText)findViewById(R.id.te_write);
    btn_start.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            string=text.getText().toString();
        Toast.makeText(MainActivity.this,string,Toast.LENGTH_SHORT).show();
            SQLiteDatabase db=base.setBase(MainActivity.this).getWrite();
            cursor=db.rawQuery("select * from mytable where age=?",new String[]{string});
            if (cursor.moveToFirst()){
                do {
                  String name=cursor.getString(cursor.getColumnIndex("name"));
                    Toast.makeText(MainActivity.this,name,Toast.LENGTH_SHORT).show();
                }while (cursor.moveToNext());
                Intent intent=new Intent(MainActivity.this,Main2Activity.class);
                startActivity(intent);
            }
            cursor.close();

        }
    });
}

@Override
protected void onDestroy() {
    super.onDestroy();

}

}

4.Main2Activity代码 也是一个button 和一个edit

public class Main2Activity extends AppCompatActivity {
EditText editText;
Button btn_write;
String age;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    init();
    btn_write.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            age=editText.getText().toString();
            SQLiteDatabase db=base.setBase(Main2Activity.this).getWrite();
            db.delete("mytable","age=?",new String[]{age});
            Intent intent=new Intent(Main2Activity.this,MainActivity.class);
            startActivity(intent);
        }
    });
}
public void init(){
    editText=(EditText)findViewById(R.id.write);
    btn_write=(Button)findViewById(R.id.btn_delete);
} }