Question

我想在sqlite中添加一个名字，一旦在sqlite中插入数据，我就会更新recyclerview。以下是我的代码

public class DbContract {
    public static final int SYNC_STATUS_OK=0;
    public static final int SYNC_STATUS_FAILED=1;
    public static final String DATABASE_NAME="contactdb";
    public static final String TABLE_NAME="contactinfo";
    public static final String NAME="name";
    public static final String SYNC_STATUS="syncstatus";
}

public class DbHelper extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION=1;
    public static final String CREATE_TABLE="create table "+DbContract.TABLE_NAME+" (id integer primary key autoincrement, "+DbContract.NAME+" text,"+
            DbContract.SYNC_STATUS+" integer);";
    public static final String DROP_TABLE="drop table if exists "+DbContract.TABLE_NAME;

    public DbHelper(Context context) {
        super(context, DbContract.DATABASE_NAME, null, DATABASE_VERSION);
    }

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

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL(DROP_TABLE);
        onCreate(sqLiteDatabase);
    }

    public void saveToLocalDatabase(String name,int syncstatus,SQLiteDatabase sqLiteDatabase){
        ContentValues contentValues=new ContentValues();
        contentValues.put(DbContract.NAME,name);
        contentValues.put(DbContract.SYNC_STATUS,syncstatus);
        sqLiteDatabase.insert(DbContract.TABLE_NAME,null,contentValues);
    }

    public Cursor readFromLocalDatabase(SQLiteDatabase sqLiteDatabase){
        String[] projection={DbContract.NAME,DbContract.SYNC_STATUS};
      //  Log.i("frff", "readFromLocalDatabase: "+projection.toString());
        return (sqLiteDatabase.query(DbContract.TABLE_NAME,projection,null,null,null,null,null));
    }

    public void updateLocalDatabase(String name, int syncstatus,SQLiteDatabase sqLiteDatabase){
        ContentValues contentValues=new ContentValues();
        contentValues.put(DbContract.SYNC_STATUS,syncstatus);
        String selection = DbContract.NAME+" LIKE ? ";
        String[] selection_args={name};
        sqLiteDatabase.update(DbContract.TABLE_NAME,contentValues,selection,selection_args);
    }
}


public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private EditText editText;
    private Button button;
    private ArrayList<Contact> arrayList;
    private RecyclerAdapter recyclerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView = findViewById(R.id.recyclerview);
        editText = findViewById(R.id.et);
        button = findViewById(R.id.button);
        arrayList = new ArrayList<>();
        recyclerAdapter = new RecyclerAdapter(arrayList);
        recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
        recyclerView.setHasFixedSize(true);
        recyclerView.setAdapter(recyclerAdapter);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String name = editText.getText().toString();
                saveToLocalStorage(name);
                editText.setText("");
            }
        });
    }

    public void submitName(View view) {

    }

    public boolean checkNetworkConnection() {
        ConnectivityManager connectivityManager = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
        return (networkInfo != null && networkInfo.isConnected());
    }

    private void readFromLocalStorage() {
        arrayList.clear();
        DbHelper dbHelper = new DbHelper(this);
        SQLiteDatabase sqLiteDatabase = dbHelper.getReadableDatabase();
        Cursor cursor = dbHelper.readFromLocalDatabase(sqLiteDatabase);
        while (cursor.moveToNext()) {
            String name = cursor.getString(cursor.getColumnIndex(DbContract.NAME));
            int sync_status = cursor.getInt(cursor.getColumnIndex(DbContract.SYNC_STATUS));
            arrayList.add(new Contact(name, sync_status));

        }
        recyclerAdapter.notifyDataSetChanged();
        cursor.close();
        dbHelper.close();
    }

    private void saveToLocalStorage(String name) {
        DbHelper dbHelper = new DbHelper(this);
        SQLiteDatabase sqLiteDatabase = dbHelper.getWritableDatabase();
        if (checkNetworkConnection()) {

        } else {
            dbHelper.saveToLocalDatabase(name, DbContract.SYNC_STATUS_FAILED, sqLiteDatabase);
        }
        readFromLocalStorage();
        dbHelper.close();
    }
}

每当通过edittext添加某个项目并且按钮被cliked时，我的recyclerview中就看不到任何项目了。我的logcat没有收到任何错误，应用程序也没有崩溃。任何帮助将不胜感激。

Answer 1

请尝试以下代码：

    public class DbContract {
    public static final int SYNC_STATUS_OK=0;
    public static final int SYNC_STATUS_FAILED=1;
    public static final String DATABASE_NAME="contactdb";
    public static final String TABLE_NAME="contactinfo";
    public static final String NAME="name";
    public static final String SYNC_STATUS="syncstatus";
    }

    public class DbHelper extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION=1;
    public static final String CREATE_TABLE="create table "+DbContract.TABLE_NAME+" id integer primary key autoincrement, "+DbContract.NAME+" text,"+
            DbContract.SYNC_STATUS+" integer);";
    public static final String DROP_TABLE="drop table if exists "+DbContract.TABLE_NAME;

    public DbHelper(Context context) {
        super(context, DbContract.DATABASE_NAME, null, DATABASE_VERSION);
    }

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

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL(DROP_TABLE);
        onCreate(sqLiteDatabase);
    }

    public void saveToLocalDatabase(String name,int syncstatus,SQLiteDatabase sqLiteDatabase){
        ContentValues contentValues=new ContentValues();
        contentValues.put(DbContract.NAME,name);
        contentValues.put(DbContract.SYNC_STATUS,syncstatus);
        sqLiteDatabase.insert(DbContract.TABLE_NAME,null,contentValues);
    }

    public Cursor readFromLocalDatabase(SQLiteDatabase sqLiteDatabase){
        String[] projection={DbContract.NAME,DbContract.SYNC_STATUS};
      //  Log.i("frff", "readFromLocalDatabase: "+projection.toString());
        return (sqLiteDatabase.query(DbContract.TABLE_NAME,projection,null,null,null,null,null));
    }

    public void updateLocalDatabase(String name, int syncstatus,SQLiteDatabase sqLiteDatabase){
        ContentValues contentValues=new ContentValues();
        contentValues.put(DbContract.SYNC_STATUS,syncstatus);
        String selection = DbContract.NAME+" LIKE ? ";
        String[] selection_args={name};
        sqLiteDatabase.update(DbContract.TABLE_NAME,contentValues,selection,selection_args);
    }
}


public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private EditText editText;
    private Button button;
    private ArrayList<Contact> arrayList;
    private RecyclerAdapter recyclerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView = findViewById(R.id.recyclerview);
        editText = findViewById(R.id.et);
        button = findViewById(R.id.button);
        arrayList = new ArrayList<>();
        recyclerAdapter = new RecyclerAdapter(arrayList);
        recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
        recyclerView.setHasFixedSize(true);
        recyclerView.setAdapter(recyclerAdapter);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String name = editText.getText().toString();
                saveToLocalStorage(name);
                editText.setText("");
            }
        });
    }

    public void submitName(View view) {

    }

    public boolean checkNetworkConnection() {
        ConnectivityManager connectivityManager = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
        return (networkInfo != null && networkInfo.isConnected());
    }

    private void readFromLocalStorage() {
        arrayList.clear();
        DbHelper dbHelper = new DbHelper(this);
        SQLiteDatabase sqLiteDatabase = dbHelper.getReadableDatabase();
        Cursor cursor = dbHelper.readFromLocalDatabase(sqLiteDatabase);
        while (cursor.moveToNext()) {
            String name = cursor.getString(cursor.getColumnIndex(DbContract.NAME));
            int sync_status = cursor.getInt(cursor.getColumnIndex(DbContract.SYNC_STATUS));
            arrayList.add(new Contact(name, sync_status));

        }
        recyclerAdapter.notifyDataSetChanged();
        cursor.close();
        dbHelper.close();
    }

    private void saveToLocalStorage(String name) {
        DbHelper dbHelper = new DbHelper(this);
        SQLiteDatabase sqLiteDatabase = dbHelper.getWritableDatabase();
        if (checkNetworkConnection()) {

        } else {
            dbHelper.saveToLocalDatabase(name, DbContract.SYNC_STATUS_FAILED, sqLiteDatabase);
        }
        dbHelper.close();
        readFromLocalStorage();

    }
}

Answer 2

为什么要检查互联网连接，你会检查吗？我想我注意到在你的代码编译器中检查连接并编译if条件并且不对数据库进行任何输入请检查一次。

在sqlite中添加项目后，RecyclerView中没有项目

2 个答案: