安卓：NullPointerException异常上getWritableDatabase（） [英] Android: NullPointerException on getWritableDatabase()

问题描述

下面是我尝试访问数据库：

Here is where I try to access the database:

UserDataAdapter dbHelper = new UserDataAdapter(this);
dbHelper.open();
dbHelper.createNetwork(network);
dbHelper.close();

UserDataAdapter.java：

UserDataAdapter.java:

public UserDataAdapter open() throws SQLException {
        dbHelper = new DatabaseHelper(context); // of class DatabaseHelper
        database = dbHelper.getWritableDatabase(); // this line!!   
        return this;
    }

DatabaseHelper.java：

DatabaseHelper.java:

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

@Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(Defines.DATABASE_CREATE_TAXI_SERVICE_DATABASE);
    }

崩溃：
09-13 18：12：33.119：电子

Crash: 09-13 18:12:33.119: E

RROR/AndroidRuntime(7488): FATAL EXCEPTION: main
09-13 18:12:33.119: ERROR/AndroidRuntime(7488): java.lang.NullPointerException
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.basind.testapp.database.UserDataAdapter.open(UserDataAdapter.java:29)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.basind.testapp.FetchNetworks.addToDatabase(FetchNetworks.java:107)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.basind.testapp.FetchNetworks.access$1(FetchNetworks.java:105)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.basind.testapp.FetchNetworks$1.onResponseReceived(FetchNetworks.java:75)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.basind.testapp.async.CallbackWrapper.run(CallbackWrapper.java:15)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at android.os.Handler.handleCallback(Handler.java:587)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at android.os.Handler.dispatchMessage(Handler.java:92)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at android.os.Looper.loop(Looper.java:145)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at android.app.ActivityThread.main(ActivityThread.java:4937)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at java.lang.reflect.Method.invokeNative(Native Method)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at java.lang.reflect.Method.invoke(Method.java:521)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-13 18:12:33.119: ERROR/AndroidRuntime(7488):     at dalvik.system.NativeStart.main(Native Method)

其他详情：

• 目标：Android的7


• 测试设备：HTC Desire的

推荐答案

确认如果你的上下文正确被设置与否。

Make sure if your Context is properly being set or not.

private Context context;
private SQLiteDatabase database;
private DatabaseHelper dbHelper;

public UserDataAdapter(Context context) {
    this.context = context;
}

public UserDataAdapter open() throws SQLException
{
    dbHelper = new DatabaseHelper(context);
    database = dbHelper.getWritableDatabase();
    return this;
}

这篇关于安卓：NullPointerException异常上getWritableDatabase（）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！