Question

当我在logcat中将数据插入sqlite数据库时，它会提示空对象引用。但是使用我在另一个程序中使用的相同代码它可以工作。我能否提出一些解决这个问题的建议。

这是我的DBControl

public void addProduct(Product product) {
    SQLiteDatabase db=this.getWritableDatabase();
    ContentValues cv=new ContentValues();

    cv.put(Code,product.getProductCode());
    cv.put(Description,product.getProductName());
    cv.put(MenuDepartment,product.getMenuDepartment());
    cv.put(CondimentGroup,product.getCondimentGroup1());
    cv.put(ModifierGroup,product.getModifierGroup1());
    //inserting row
    db.insert(mproduct, null, cv);
    //close the database to avoid any leak
    db.close();
}

这是按钮点击时插入数据的方式。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_printer_test_demo);
    innitView();

}
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_printer_test_demo);
    innitView();

}


private void innitView() {


    new BitmapUtils(this);
    b_table = (Button) findViewById(R.id.b_table);
    b_additem = (Button)findViewById(R.id.additem);
    findViewById(R.id.additem).setOnClickListener(this);
    findViewById(R.id.b_exit).setOnClickListener(this);
    b_additem.setOnClickListener(this);
    b_table.setOnClickListener(this);

    info = (TextView) findViewById(R.id.info);

    callback = new ICallback.Stub() {

        @Override
        public void onRunResult(final boolean success) throws RemoteException {
        }

        @Override
        public void onReturnString(final String value) throws RemoteException {
            Log.i(TAG,"printlength:" + value + "\n");
        }

        @Override
        public void onRaiseException(int code, final String msg) throws RemoteException {
            Log.i(TAG,"onRaiseException: " + msg);
            runOnUiThread(new Runnable(){
                @Override
                public void run() {
                    info.append("onRaiseException = " + msg + "\n");
                }});

        }
    };

    setButtonEnable(false);

    Intent intent=new Intent();
    intent.setPackage("woyou.aidlservice.jiuiv5");
    intent.setAction("woyou.aidlservice.jiuiv5.IWoyouService");
    startService(intent);
    bindService(intent, connService, Context.BIND_AUTO_CREATE);
}

private void setButtonEnable(boolean flag){


    b_table.setEnabled(flag);
    b_additem.setEnabled(flag);

}


@Override
public void onClick(View v) {
        switch (v.getId()) {

        case R.id.b_table:
            //打印表格
            printTable();
            break;
        case R.id.additem:
                additem();
            break;

        }
}

public void additem(){
        try {

                    DBControl db = new DBControl(context);<------the logcat show the error at here
                    db.addProduct(new Product("10001", "Nasi Lemak", "A", "C1", "M1"));
                    db.addProduct(new Product("10002", "STEAM LOTUS LEAF GLUTINOUS RICE", "A", "C1", "M1"));
                    db.addProduct(new Product("10003", "EIGHT TREASURE GLUTINOUS RICE", "B", "C2", "M2"));
                    db.addProduct(new Product("10004", "CHICKEN PORRIDGE & DRIED SCALLOP", "B", "C2", "M2"));
                    db.addProduct(new Product("10005", "FISH PORRIDGE", "C", "C3", "M3"));
                    db.addProduct(new Product("10006", "LAKSA", "C", "C3", "M3"));
            }catch(SQLiteException e){
                        e.printStackTrace();
            }
}

logcat的

  java.lang.NullPointerException: Attempt to invoke virtual method 'void com.test.printertestdemo.DBControl.addProduct(com.test.printertestdemo.Constructor.Product)' on a null object reference
                  at com.test.printertestdemo.PrinterTestDemoAct.additem(PrinterTestDemoAct.java:181)
                  at com.test.printertestdemo.PrinterTestDemoAct.onClick(PrinterTestDemoAct.java:173)
                  at android.view.View.performClick(View.java:4848)
                  at android.view.View$PerformClick.run(View.java:20262)
                  at android.os.Handler.handleCallback(Handler.java:815)
                  at android.os.Handler.dispatchMessage(Handler.java:104)
                  at android.os.Looper.loop(Looper.java:194)
                  at android.app.ActivityThread.main(ActivityThread.java:5637)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:372)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:960)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

Answer 1

on your create define

Context context = getContext();

调用方法项传递上下文

addItem(context);

在你的方法中添加参数Context context; 那就行了。

如果不起作用，请使用

Activity context = getActivity();

第一步。希望它有所帮助。

将数据插入sqlite数据库时的Android null对象引用

1 个答案: