2

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但同时在表类中使用数据库类实例并运行应用程序时，一切正常当控制转到getwritabledatabase我得到异常并退出应用程序时，下面是所有 3 个类的代码。

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getwritabledatabase从活动类转到数据库类时，它正在执行，但是当从库存表类的控制转到数据库类并执行getwritabledatabase异常之后，不幸的是我无法在此处粘贴异常。

谁能帮我解决这个问题？

日志猫

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
4

5 回答 5

1

你应该替换这个

String select="Select StockID from Stocktable";

和

String select="Select Stock_ID from Stocktable";

并且还初始化了你的Context C1. 创建将电流传递Context给StockTable类似的构造函数：

public StockTable(Context cxnt){
this.c1=cxnt;
d1=new Database(c1);
 }

并添加这个

 StockTable st=new StockTable(this);

进入你的stockmanager活动。

于 2014-02-06T06:12:22.123 回答
1

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

我只是编辑你的 StockTable.java 试试这个

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

    }

}
于 2014-02-06T06:17:12.573 回答
0

StockID&Stock_ID 是两个不同的列名。

在创建您Stock_ID用作列的表和触发您StockID用作列的选择查询时，这是您的错误。您的查询应该是

String select="Select Stock_ID from Stocktable";

并且还初始化了你的Context C1. 创建将电流传递Context给StockTable类似的构造函数：

public StockTable(Context cxnt){
this.c1=cxnt;
 }
于 2014-02-06T06:09:21.557 回答
0

当你实例化 StockTable 时，这两行是个问题：

Context c1;
Database d1=new Database(c1);

c1 未初始化.. 没有创建数据库的上下文。将有效上下文传递给您的构造函数，或使用“set”方法，然后实例化您的数据库以供使用。像这样：

public StockTable(Context context) {
 c1 = context;
 d1=new Database(c1);
}

我会替换：

String select="Select StockID from Stocktable";

和：

String select="Select "+  column1 + " from " + tablename;
于 2014-02-06T06:12:55.543 回答
0

每当您使用数据库和助手时， 

Database database = new Database(this);

在 onCreate() 之前，您不能将类实例用作上下文。将您的数据库和数据库初始化推迟到 onCreate() 或更高版本。

也参考这些，以更好地理解它：

SQlite 数据库：无法找到
SQLiteOpenHelper.getWritableDatabase() 的上下文 nullPointerException，Android

于 2014-02-06T06:18:15.087 回答