在Android中执行getwritabledatabase()时出错 [英] Getting error while executing getwritabledatabase() in android

问题描述

我为数据库创建了一个类，为表和多个活动类创建了多个类，当我在活动类中使用数据库类实例时，一切正常，但同时在表类中使用数据库类实例并运行控件转到getwritabledatabase时，我的应用程序出现异常，并且退出了应用程序，下面是所有3个类的代码.

I have created one class for database and multiple classes for tables and multiple activity classess everything works fine when I use the database class instance in activity class but at the same time when I use the database class instance in table class and run the application as soon as the control goes to getwritabledatabase I am getting exception and application is exited, below is the code for all 3 classes.

数据库类.

public class Database extends SQLiteOpenHelper{

    private static  String dbname="Manager";
    private static int dbversion=2;
    SQLiteDatabase db;

    public Database(Context context) {

        super(context, dbname, null, dbversion);
        // TODO Auto-generated constructor stub
        db=this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        StockTable st=new StockTable();
        db.execSQL(st.stocktable);
        }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

活动课

public class stockmanager extends Activity{

    String getentry=null;
    Database d=new Database(this);
    StockTable st=new StockTable();


    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.stockmanager);

    final Button AddStock=(Button) findViewById(R.id.button1);
        final EditText entry=(EditText) findViewById(R.id.editText1);
        final Button BroDetail=(Button) findViewById(R.id.button2);

        AddStock.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                getentry=entry.getText().toString();
                d.db.insert(st.tablename, null,st.insert());


            }
        });
                }
}

表类

    public class StockTable {

    Context c1;
    Database d1=new Database(c1);
    final String tablename="StockTable";
    private String column1="Stock_ID";
    private String column2="StockName";


    final String stocktable = "CREATE TABLE " + tablename + 
                " (" + column1+ " INTEGER PRIMARY KEY , " + column2 + " TEXT) ";

    public ContentValues insert(){

String select="Select StockID from Stocktable";

d.db.execsql(select);
        ContentValues cvi=new ContentValues();
        for(int i=0;i<=sm.getentry.length();i++)
        {
            cvi.put(column1, 1);
            cvi.put(column2,sm.getentry);
                        }

        return cvi;
    }

    public void delete(){


    }

首先，当控制权从活动类转到数据库类的getwritabledatabase时，它正在执行，但是当股票表类中的控制权转到数据库类并执行getwritabledatabase时，发生了例外，很遗憾，我无法粘贴异常在这里.

First when control goes to getwritabledatabase of database class from activity class then it is executing but after when control from stock table class goes to database class and executes getwritabledatabase exception is occurred, Unfortunately I am unable to paste the exceptions here.

有人可以帮我解决这个问题吗?

Can anyone please help me to solve this ?

Logcat

02-07 10:06:09.624: D/libEGL(10756): loaded /system/lib/egl/libEGL_genymotion.so
02-07 10:06:09.628: D/(10756): HostConnection::get() New Host Connection established 0xb87f5e00, tid 10756
02-07 10:06:09.720: D/libEGL(10756): loaded /system/lib/egl/libGLESv1_CM_genymotion.so
02-07 10:06:09.748: D/libEGL(10756): loaded /system/lib/egl/libGLESv2_genymotion.so
02-07 10:06:10.024: W/EGL_genymotion(10756): eglSurfaceAttrib not implemented
02-07 10:06:10.044: E/OpenGLRenderer(10756): Getting MAX_TEXTURE_SIZE from GradienCache
02-07 10:06:10.196: E/OpenGLRenderer(10756): Getting MAX_TEXTURE_SIZE from Caches::initConstraints()
02-07 10:06:10.212: D/OpenGLRenderer(10756): Enabling debug mode 0
02-07 10:07:17.328: W/EGL_genymotion(10756): eglSurfaceAttrib not implemented
02-07 10:07:19.820: I/Choreographer(10756): Skipped 36 frames!  The application may be doing too much work on its main thread.
02-07 10:07:22.556: W/EGL_genymotion(10756): eglSurfaceAttrib not implemented
02-07 10:07:22.788: I/Choreographer(10756): Skipped 44 frames!  The application may be doing too much work on its main thread.
02-07 10:07:28.064: D/dalvikvm(10756): GC_FOR_ALLOC freed 105K, 1% free 16944K/17072K, paused 37ms, total 40ms
02-07 10:07:30.524: I/System.out(10756): asdfdw
02-07 10:07:30.576: D/AndroidRuntime(10756): Shutting down VM
02-07 10:07:30.612: W/dalvikvm(10756): threadid=1: thread exiting with uncaught exception (group=0xa4b6e648)
02-07 10:07:30.652: E/AndroidRuntime(10756): FATAL EXCEPTION: main
02-07 10:07:30.652: E/AndroidRuntime(10756): android.database.sqlite.SQLiteException: unknown error (code 0): Queries can be performed using SQLiteDatabase query or rawQuery methods only.
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.database.sqlite.SQLiteConnection.nativeExecuteForChangedRowCount(Native Method)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.database.sqlite.SQLiteConnection.executeForChangedRowCount(SQLiteConnection.java:734)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.database.sqlite.SQLiteSession.executeForChangedRowCount(SQLiteSession.java:754)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.database.sqlite.SQLiteStatement.executeUpdateDelete(SQLiteStatement.java:64)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1674)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1603)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at com.example.portfoliomanager.StockTable.insert(StockTable.java:43)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at com.example.portfoliomanager.stockmanager$1.onClick(stockmanager.java:36)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.view.View.performClick(View.java:4240)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.view.View$PerformClick.run(View.java:17721)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.os.Handler.handleCallback(Handler.java:730)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.os.Looper.loop(Looper.java:137)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at android.app.ActivityThread.main(ActivityThread.java:5103)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at java.lang.reflect.Method.invokeNative(Native Method)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at java.lang.reflect.Method.invoke(Method.java:525)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-07 10:07:30.652: E/AndroidRuntime(10756):    at dalvik.system.NativeStart.main(Native Method)
02-07 10:07:34.288: I/Process(10756): Sending signal. PID: 10756 SIG: 9
02-07 10:07:36.624: D/libEGL(10871): loaded /system/lib/egl/libEGL_genymotion.so
02-07 10:07:36.644: D/(10871): HostConnection::get() New Host Connection established 0xb87f5e70, tid 10871
02-07 10:07:36.784: D/libEGL(10871): loaded /system/lib/egl/libGLESv1_CM_genymotion.so
02-07 10:07:36.784: D/libEGL(10871): loaded /system/lib/egl/libGLESv2_genymotion.so
02-07 10:07:37.104: W/EGL_genymotion(10871): eglSurfaceAttrib not implemented
02-07 10:07:37.108: E/OpenGLRenderer(10871): Getting MAX_TEXTURE_SIZE from GradienCache
02-07 10:07:37.132: E/OpenGLRenderer(10871): Getting MAX_TEXTURE_SIZE from Caches::initConstraints()
02-07 10:07:37.132: D/OpenGLRenderer(10871): Enabling debug mode 0

推荐答案

错误是因为您尝试使用空上下文访问数据库.因此，在传递给数据库构造函数之前，您需要初始化c1.

Error is because you trying to access database with null context. So you need to initialize c1 before passing to Database constructor.

我只是编辑您的StockTable.java试试这个

I just Edit your StockTable.java try this

import android.content.ContentValues;
import android.content.Context;

public class StockTable {

    Context c1;
    Database d1;
    final String tablename = "StockTable";
    private String column1 = "Stock_ID";
    private String column2 = "StockName";

    final String stocktable = "CREATE TABLE " + tablename + " (" + column1 + " INTEGER PRIMARY KEY , " + column2 + " TEXT) ";


    public StockTable(Context mContext){
        c1= mContext;
        d1= new Database(c1);
    }
    public ContentValues insert() {


        ContentValues cvi = new ContentValues();
        for (int i = 0; i <= sm.getentry.length(); i++) {
            cvi.put(column1, 1);
            cvi.put(column2, sm.getentry);
        }

        return cvi;
    }

    public void delete() {

    }
}

如何使用?

public class stockmanager extends Activity {

    String getentry = null;
    Database d;
    StockTable st;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.stockmanager);

        d = new Database(this.getApplicationContext());
        st = new StockTable(this.getApplicationContext());

        final Button AddStock = (Button) findViewById(R.id.button1);
        final EditText entry = (EditText) findViewById(R.id.editText1);
        final Button BroDetail = (Button) findViewById(R.id.button2);

        AddStock.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                getentry = entry.getText().toString();
                d.db.insert(st.tablename, null, st.insert());

            }
        });
    }
}

更新您的数据库类

public class Database extends SQLiteOpenHelper {

    private static String dbname = "Manager";
    private static int dbversion = 2;
    SQLiteDatabase db;
    private Context mContext;

    public Database(Context context) {

        super(context, dbname, null, dbversion);
        // TODO Auto-generated constructor stub
        mContext = context;
        db = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        StockTable st = new StockTable(mContext);
        db.execSQL(st.stocktable);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

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