Question

我遇到了SQLite问题。我一直在开发我的连接设备，而不是模拟器。这一直很好。我已经在手机和平板电脑上多次构建和安装了应用程序。大约一周前，我对我的资产文件夹中的SQLite数据库进行了更改。我从我的设备上卸载了应用程序，因为我想要一个干净的安装，但现在好像数据库永远不会到达那里。这是一直存在的相同代码。这种事情：

请查看新代码样本的底部

private static String _DB_PATH = "/data/data/com.android.myapp/databases/";
private static final String _DATABASE_NAME = "myapp.sqlite";

private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;
    try {
        String myPath = _DB_PATH + _DATABASE_NAME;


        ***//THE PROBLEM IS THIS LINE, FOR WHATEVER REASON IT'S NO LONGER FINDING THE DATABASE IN THE ASSETS FOLDER
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);***


    } 
    catch (SQLiteException e) {
        //database does't exist yet.
    }
    if (checkDB != null) checkDB.close();

    return checkDB != null ? true : false;
}

public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();
    if (dbExist) {
        //do nothing - database already exist
    } 
    else {
        //By calling this method and empty database will be created into the default system path
        //of your application so we are gonna be able to overwrite that database with our database.
        try {
            getReadableDatabase();
            copyDataBase();
        } 
        catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}

它安装时没有错误，但是当我做某事来访问设备上的数据库时，它会轰炸getReadableDatabase（）;.

这是LogCat：

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.myapp/com.android.myapp.ActivityL}:                 
java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1748)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1764)
at android.app.ActivityThread.access$1500(ActivityThread.java:122)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1002)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:132)
at android.app.ActivityThread.main(ActivityThread.java:4025)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:491)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
at dalvik.system.NativeStart.main(Native Method)
11-09 21:55:26.250: E/AndroidRuntime(11474): Caused by: java.lang.NullPointerException
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:149)
at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:223)
at com.yesjapan.android.database.DatabaseHelper.createDataBase(DatabaseHelper.java:82)
at com.yesjapan.android.database.DbAdapter.open(DbAdapter.java:71)
at com.android.myapp.FragmentP.LoadC(FragmentP.java:226)
at com.android.myapp.FragmentP.onCreateView(FragmentP.java:97)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:735)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:926)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:909)
at android.app.FragmentManagerImpl.dispatchStart(FragmentManager.java:1584)
at android.app.Activity.performStart(Activity.java:4377)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1721)

我可以安装以前的版本，它似乎工作。我已经删除并从头开始重建数据库。我不知道为什么它不认为那里有数据库或数据库没有安装的原因。

如果要编写代码，花时间在这个垃圾上真是令人沮丧！ arrgh！

编辑：这是另一个常见错误

11-10 17:33:55.983: E/Database(22087): sqlite3_open_v2("/data/data/com.android.myapp/databases/myapp.sqlite", &handle, 2, NULL) failed

编辑：新代码示例

private boolean checkDataBase() {
    //SQLiteDatabase checkDB = null;
    File dbfile = null;
    try {
        //String myPath = _DB_PATH + _DATABASE_NAME;
        //File myPath = _helperContext.getDatabasePath(_DATABASE_NAME);
        //checkDB = SQLiteDatabase.openDatabase(myPath.toString(), null, SQLiteDatabase.OPEN_READWRITE);

        String myPath = _DB_PATH + _DATABASE_NAME;
        dbfile = new File(myPath);
        //checkdb = SQLiteDatabase.openDatabase(myPath,null,SQLiteDatabase.OPEN_READWRITE);
    } catch (SQLiteException e) {
        Log.e("DatabaseHelper", e.getMessage());
    }
    //if (checkDB != null) checkDB.close();

    return dbfile.exists();         
    //return checkDB != null;
}

public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();
    if (dbExist) {
        //do nothing - database already exist
    } 
    else {
        //By calling this method and empty database will be created into the default system path
        //of your application so we are gonna be able to overwrite that database with our database.
        getReadableDatabase();
        try {
            copyDataBase();
        } 
        catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}

Answer 1

运行unzip -l <your_app.apk>并确保包含数据库。如果不存在，请尝试进行干净的构建。

Answer 2

首先从不硬编码路径，因为不同的OEM可以随时更改您的应用无法使用getDatabasePath()

Answer 3

嗨请重新下线。在你的代码中

checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

而不是

checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

由于

Android应用安装不包括SQLite数据库

3 个答案: