Undefined variable: dataProvider in yii2

Question

Need help in Undefined variable: dataProvider in yii2 I have installed kartik gridview extension. I am new in YII2. trying to build the grid. Please help.

Getting Following error
PHP Notice – yii\base\ErrorException Undefined variable: dataProvider

Here is my Controller Code

echo GridView::widget([
        'dataProvider' => $dataProvider,
        'filterModel' => $searchModel,
        'columns' => $gridColumns,
        'containerOptions' => ['style'=>'overflow: auto'], // only set when $responsive = false
        'beforeHeader'=>[
            [
                'columns'=>[
                    ['content'=>'Header Before 1', 'options'=>['colspan'=>4, 'class'=>'text-center warning']], 
                    ['content'=>'Header Before 2', 'options'=>['colspan'=>4, 'class'=>'text-center warning']], 
                    ['content'=>'Header Before 3', 'options'=>['colspan'=>3, 'class'=>'text-center warning']], 
                ],
                'options'=>['class'=>'skip-export'] // remove this row from export
            ]
        ],
        'toolbar' =>  [
            ['content'=>
                Html::button('<i class="glyphicon glyphicon-plus"></i>', ['type'=>'button', 'title'=>Yii::t('kvgrid', 'Add Book'), 'class'=>'btn btn-success', 'onclick'=>'alert("This will launch the book creation form.\n\nDisabled for this demo!");']) . ' '.
                Html::a('<i class="glyphicon glyphicon-repeat"></i>', ['grid-demo'], ['data-pjax'=>0, 'class' => 'btn btn-default', 'title'=>Yii::t('kvgrid', 'Reset Grid')])
            ],
            '{export}',
            '{toggleData}'
        ],
        'pjax' => true,
        'bordered' => true,
        'striped' => false,
        'condensed' => false,
        'responsive' => true,
        'hover' => true,
        'floatHeader' => true,
        'floatHeaderOptions' => ['scrollingTop' => $scrollingTop],
        'showPageSummary' => true,
        'panel' => [
            'type' => GridView::TYPE_PRIMARY
        ],
    ]);

Answer 1

In your controller you must pass all the variables that must appear in the view to the render method you call at the end of the controller:

return $this->render('viewName', [
    'dataProvider' => $dataProvider,
    // ... Other fields
]);

Or you can call compact() like this:

return $this->render('viewName', compact('dataProvider'));

See also: Yii2 actions

Hope this helps.