[英]Android Studio: SQLite database doesn't create
我目前正在为自己构建一个密码管理器应用程序。 我计划将密码保存在 SQLite 数据库中。 为此,我使用此代码:
package com.example.passwordmanager;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import androidx.annotation.Nullable;
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String COLUMN_PASSWORD = "password";
public static final String PASSWORDS_TABLE = COLUMN_PASSWORD + "s_table";
public static final String COLUMN_ID = "id";
public static final String COLUMN_SERVICE = "service";
public static final String COLUMN_CREATION_DATE = "creation_date";
public static final String COLUMN_USED_NAME = "used_name";
public static final String COLUMN_USED_EMAIL = "used_email";
public DatabaseHelper(@Nullable Context context) {
super(context, "passwordManager.db", null,1);
Log.d("DatabaseHelper","Constructor reached");
}
@Override
public void onCreate(SQLiteDatabase db) {
String createTableStatement = "CREATE TABLE "+ PASSWORDS_TABLE + " ( " + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_SERVICE + " VARCHAR(40), " + COLUMN_PASSWORD + " VARCHAR(40), " + COLUMN_CREATION_DATE + " VARCHAR(11), " + COLUMN_USED_NAME + " VARCHAR(40), " + COLUMN_USED_EMAIL + " VARCHAR(40), master VARCHAR(20), firstTime BOOLEAN)";
Log.d("DatabaseHelper","OnCreate1 reached");
db.execSQL(createTableStatement);
Log.d("DatabaseHelper","OnCreate2 reached");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+PASSWORDS_TABLE);
onCreate(db);
}
public boolean addToTable(Registration profile){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COLUMN_PASSWORD,profile.hashedPassword);
cv.put(COLUMN_SERVICE,profile.service);
cv.put(COLUMN_CREATION_DATE,profile.creation_date);
cv.put(COLUMN_USED_NAME,profile.used_name);
cv.put(COLUMN_USED_EMAIL,profile.used_email);
long insert = db.insert(PASSWORDS_TABLE, null, cv);
if(insert==-1){
return true;
}else{
return false;
}
}
}
这段代码的问题是,它只是没有在 data\\data\\com.example.passwordmanager 中创建数据库或数据库文件夹。 我尝试输出调用构造函数时它将到达的方法,但我意识到它永远不会到达 onCreate 方法。
DatabaseHelper 类只被调用一次,以便:
package com.example.passwordmanager;
import androidx.appcompat.app.AppCompatActivity;
import android.app.Application;
import android.content.Context;
import android.content.Intent;
import android.hardware.input.InputManager;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.Toast;
public class CreatingNewEntryActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_creating_new_entry);
DatabaseHelper dh = new DatabaseHelper(CreatingNewEntryActivity.this);
}
这是代码的问题吗? 我是否必须在 manifest.xml 中授予权限? 我在模拟器上搞砸了吗? 该应用程序启动正常,只是不创建数据库。
您需要在数据库助手上调用getWritableDatabase()
或getReadableDatabase()
以使框架创建数据库文件并触发onCreate()
。 仅仅调用构造函数是不够的。
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