代码之家 › 专栏 › 技术社区 › Karim Mtl

android创建sqlite数据库

android-sqlite sqlite android

Karim Mtl · 技术社区 · 7 年前

我无法使用简单的文件来创建sqlite数据库。如果数据库已创建或升级,但没有显示,我将在日志中记录一些希望在日志中显示的消息。

代码如下:

package com.example.karim.myandoidapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class HomeActivity extends AppCompatActivity {

    String msg = "My android app log : ";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.e(msg, "onCreate() event loading activity_home view");
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
        Log.e(msg, "onCreate() event loading activity_home view");
        Context context = myandoidapp.getAppContext();
        MySQLiteHelper MySQLiteHelper = new MySQLiteHelper(context);
    }

    private class MySQLiteHelper extends SQLiteOpenHelper {

        // Database Version
        private static final int DATABASE_VERSION = 1;
        // Database Name
        private static final String DATABASE_NAME = "mydbnamesss";

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

        @Override
        public void onCreate(SQLiteDatabase db) {
            Log.e("DEBUG: ", "db created at " + db.getPath());
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.e("DEBUG: ", "db upgraded ");
        }

    }

}

以下是我日志中的输出:

06-14 15:02:29.122 6644-6644/com.example.karim.myandoidapp E/MyÂ androidÂ appÂ logÂ :: Opening HomeActivity

    --------- beginning of system
06-14 15:02:29.141 6644-6644/com.example.karim.myandoidapp E/MyÂ androidÂ appÂ logÂ :: onCreate() event loading activity_home view
06-14 15:02:29.203 6644-6673/com.example.karim.myandoidapp D/EGL_emulation: eglMakeCurrent: 0xa22050c0: ver 3 0 (tinfo 0xa2203360)
06-14 15:02:29.209 6644-6673/com.example.karim.myandoidapp D/EGL_emulation: eglMakeCurrent: 0xa22050c0: ver 3 0 (tinfo 0xa2203360)
06-14 15:02:29.216 6644-6673/com.example.karim.myandoidapp D/EGL_emulation: eglMakeCurrent: 0xa22050c0: ver 3 0 (tinfo 0xa2203360)
06-14 15:02:29.218 6644-6673/com.example.karim.myandoidapp D/OpenGLRenderer: endAllActiveAnimators on 0x8eeae180 (RippleDrawable) with handle 0xa2203ac0

我在这里补充一下,如果上下文相关,我将如何获取上下文:

包com.example.karim.myandoidapp;

导入android.content.context; 导入android.app.application;

public class myandoidapp extends Application {

    private static Context context;

    public void onCreate() {
        super.onCreate();
        myandoidapp.context = getApplicationContext();
    }

    public static Context getAppContext() {
        return myandoidapp.context;
    }

}

谢谢

2 回复 | 直到 7 年前

MikeT 7 年前

onCreate

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

    public MySQLiteHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.getWritableDatabase(); //<<<< this.getReadableDatabase could also be used.  
    }

    public MySQLiteHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        SQLiteDatabase mydb = this.getWritableDatabase();
        mydb.close();
    }

然后在实例化数据库助手时,使用 MySQLiteHelper MySQLiteHelper = new MySQLiteHelper(context);

注意, 方法在数据库的生存期内只调用一次,因此您将只在第一次打开数据库时获取日志消息。

onUpgrade

mtrewartha 7 年前

您的代码定义了 SQLiteOpenHelper 然后实例化它,但这不足以创建/打开一个sqlite数据库。如果我是你,我会在谷歌的新图书馆里读到 Room 存取资料表