Question

我一直在尝试将Spinner的静态数据存储到我的数据库中。我静态地设置了文本，click事件也没有读取数据。

这是我的代码：

ManageUsersActivity.java

public class ManageUsersActivity extends Activity implements View.OnClickListener{

DatabaseHelper helper;
EditText userName,userPassword, userId;
Spinner spinUserType;
String spinValue;
Button btnAddNewUser, btnEditUser, btnDelUser, btnViewAllUser;

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

    helper=new DatabaseHelper(this);

    userName=(EditText)findViewById(R.id.userName);
    userPassword=(EditText)findViewById(R.id.userPassword);
    btnAddNewUser=(Button)findViewById(R.id.btnAddNewUser);
    btnEditUser=(Button)findViewById(R.id.btnEditUser);
    btnDelUser=(Button)findViewById(R.id.btnDelUser);
    btnViewAllUser=(Button)findViewById(R.id.btnViewAllUser);
    spinUserType=(Spinner)findViewById(R.id.spinUserType);

    spinUserType.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener(){
        public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3){
            if(spinUserType.getSelectedItem().equals("Rector")){
                spinValue="Rector";
            }
            else if(spinUserType.getSelectedItem().equals("Student")){
                spinValue="Student";
            }
        }

        public void onNothingSelected(AdapterView<?> arg0){
            spinValue="Rector";
        }
    });

    btnAddNewUser.setOnClickListener(this);
    btnEditUser.setOnClickListener(this);
    btnDelUser.setOnClickListener(this);
    btnViewAllUser.setOnClickListener(this);
}

public void onClick(View v){
    if(v == btnAddNewUser){
        if(userName.getText().toString().trim().length()==0||
                userPassword.getText().toString().trim().length()==0)
        {
            showMessage("Error", "Please enter all values");
            return;
        }
    }

    boolean isInserted = helper.insertUserValue(userId.getText().toString(), userName.getText().toString(),
            userPassword.getText().toString(), spinValue);

    if(isInserted){
        Toast.makeText(ManageUsersActivity.this,"Data Inserted",Toast.LENGTH_SHORT).show();
    }
    else{
        Toast.makeText(ManageUsersActivity.this,"Data Not Inserted",Toast.LENGTH_SHORT).show();
    }
    clearText();
}

public void showMessage(String title,String message)
{
    AlertDialog.Builder builder=new AlertDialog.Builder(this);
    builder.setCancelable(true);
    builder.setTitle(title);
    builder.setMessage(message);
    builder.show();
}

public void clearText()
{
    userName.setText("");
    userPassword.setText("");
    userName.requestFocus();
}
  }

这是我的 DatabaseHelper.java

public class DatabaseHelper extends SQLiteOpenHelper {

// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "mmsDB";

//Tables Names
private static final String TABLE_ADMIN="admin_tbl";
private static final String TABLE_USER="user_tbl";

//Columns of TABLE_ADMIN
private static final String ADMIN_ID="a_id";
private static final String ADMIN_NAME="a_name";
private static final String ADMIN_PASSWORD="a_password";

//Columns of TABLE_USER
private static final String USER_ID="u_id";
private static final String USER_NAME="u_name";
private static final String USER_PASSWORD="u_password";
private static final String USER_TYPE="u_type";

// Create statements for Tables
private static final String CREATE_TABLE_ADMIN = "CREATE TABLE "+ TABLE_ADMIN +
        "("+ADMIN_ID+" INTEGER PRIMARY KEY AUTOINCREMENT, "
        +ADMIN_NAME+" TEXT, "
        +ADMIN_PASSWORD+" TEXT" + ")";

private static final String CREATE_TABLE_USER = "CREATE TABLE "+ TABLE_USER +
        "("+USER_ID+" INTEGER PRIMARY KEY AUTOINCREMENT, "
        +USER_NAME+" TEXT, "
        +USER_PASSWORD+" TEXT, "
        +USER_TYPE+" TEXT" + ")";

public DatabaseHelper(Context context){
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // Creating tables

    db.execSQL(CREATE_TABLE_ADMIN);
    db.execSQL("insert into " +TABLE_ADMIN+ "(" + ADMIN_ID + ","
            + ADMIN_NAME + "," +ADMIN_PASSWORD+") values(1,'admin','root')");

    db.execSQL(CREATE_TABLE_USER);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // On upgrade drop older tables
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_ADMIN);
    db.execSQL("DROP TABLE IF EXISTS "+TABLE_USER);
    // Create new tables
    onCreate(db);
}

// admin_tbl methods

public Cursor getAllAdminValues(){
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("select * from "+TABLE_ADMIN,null);
    return res;
}

// user_tbl methods

public boolean insertUserValue(String u_id, String u_name, String u_password, String u_type){
    //Inserting Records
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues contentValues=new ContentValues();
    contentValues.put(USER_ID, u_id);
    contentValues.put(USER_NAME,u_name);
    contentValues.put(USER_PASSWORD,u_password);
    contentValues.put(USER_TYPE,u_type);
    long result = db.insert(TABLE_USER,null,contentValues);

    if(result == -1){
        return false;
    }
    else{
        return true;
    }
}

public Cursor getAllRectorValues(){
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("",null);
    return res;
}

public Cursor getAllStudentValues(){
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor res = db.rawQuery("",null);
    return res;
}
}

这是我的 Logcat

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.mms, PID: 10637
              java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
                  at com.mms.ManageUsersActivity.onClick(ManageUsersActivity.java:68)
                  at android.view.View.performClick(View.java:5269)
                  at android.view.View$PerformClick.run(View.java:21556)
                  at android.os.Handler.handleCallback(Handler.java:815)
                  at android.os.Handler.dispatchMessage(Handler.java:104)
                  at android.os.Looper.loop(Looper.java:207)
                  at android.app.ActivityThread.main(ActivityThread.java:5769)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)

Answer 1

您是否尝试将用户实际点击的微调器的内容分配给您要插入的spinValue字符串？像

这样的东西

spinValue = spinUserType.getSelectedItem().toString();

Answer 2

问题出在这里：

boolean isInserted = helper.insertUserValue(userId.getText().toString(), userName.getText().toString(),
        userPassword.getText().toString(), spinValue);

您尚未初始化Editext userId

首先尝试在onCreate()初始化

userId=(EditText)findViewById(R.id.userId);

Answer 3

在手机中安装apk后，我添加了新表格（将其用作虚拟设备）每次修改数据库时，我们都需要手动增加DATABASE_VERSION。

Spinner数据不会插入SQLite数据库中

3 个答案: