Question

我创建了一个方法，它给了我一个Cursor对象，我尝试使用它来填充listview，当我在onCreate中调用该方法时，或者在按钮单击它时给我NullPointerException。表创建，我试图通过界面填充它之前我创建了Cursor函数并且正在工作，我无法理解为什么它给了我这个错误，我验证了视图和意图发送者到这个类，只有当我使用该方法会抛出此异常

 06-01 18:30:43.361    3430-3430/com.example.george.myfirstaplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.george.myfirstaplication/com.example.george.myfirstaplication.Genoflexiuni}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2351)
        at `enter code here`android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2403)
        at android.app.ActivityThread.access$600(ActivityThread.java:165)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:194)
        at android.app.ActivityThread.main(ActivityThread.java:5370)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at com.example.george.myfirstaplication.Genoflexiuni.populateListView(Genoflexiuni.java:88)
        at com.example.george.myfirstaplication.Genoflexiuni.onCreate(Genoflexiuni.java:62)
        at android.app.Activity.performCreate(Activity.java:5122)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1146)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2315)

这是方法

    public Cursor getAllGenoflexiuni(){

    SQLiteDatabase sqLiteDatabase = helper.getWritableDatabase();
    String[] columns = {DataBaseHelper.DATE_TIME, DataBaseHelper.GREUTATE_EXERCITIU, DataBaseHelper.NUMBER_SETURI, DataBaseHelper.NUMBER_REPETITIONS};
    Cursor cursor = sqLiteDatabase.query(DataBaseHelper.GENOFLEXIUNI_TABLE, columns, null, null, null, null, null);
    if(cursor != null)
    {
        cursor.moveToFirst();
    }
    return cursor;
}

这里我想用它

private String geDateTime(){
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
    Date date = new Date();
    return dateFormat.format(date);

}



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.genoflexiuni);
    weightText=(EditText)findViewById(R.id.weightText);
    setsText=(EditText)findViewById(R.id.setsText);
    repetitionsText=(EditText)findViewById(R.id.repetitionsText);
    insertButton = (Button)findViewById(R.id.insertButton);
    listView=(ListView)findViewById(R.id.listElemente);
    populateListView();


    insertButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String weight = weightText.getText().toString();
            String sets = setsText.getText().toString();
            String repetitions = repetitionsText.getText().toString();
            String dateTime = geDateTime();

            long id = helper.insertGenoflexiuni(dateTime, weight, sets, repetitions);
            if (id > 0)
                System.out.println("Succes MADAFAKAAAAA");
            else
                System.out.println("Failed miserably");

            populateListView();
        }
    });


}

private void populateListView(){
    Cursor cursor = helper.getAllGenoflexiuni();
    String[] campuri = {HelperOwner.DataBaseHelper.DATE_TIME, HelperOwner.DataBaseHelper.GREUTATE_EXERCITIU, HelperOwner.DataBaseHelper.NUMBER_SETURI, HelperOwner.DataBaseHelper.NUMBER_REPETITIONS};
    int[] id = {R.id.dateView, R.id.weightViewItem, R.id.setsViewItem, R.id.repetitionsViewItem};
    SimpleCursorAdapter myCursorAdapter;
    myCursorAdapter = new SimpleCursorAdapter(getBaseContext(),R.layout.inregistrare_exercitiu,cursor,campuri,id,0);
    listView.setAdapter(myCursorAdapter);

}

}

Answer 1

您已忘记初始化帮助实例，因为您尝试拨打getAllGenoflexiuni()并将getBaseContext()更改为Genoflexiuni.this < / p>

NullPointerException在onCreate中调用方法时的Android，

1 个答案: