AlertDialog的自定义方法抛出“试图在空对象引用上调用…” Android

Question

I've created a custom AlertDialog which has an ImageView , 3 TextView and a Button to dismiss the dialog. I need to set the ImageView and the 3 TextView 's text from my Activity , So inside the custom AlertDialog class I've created the following method:

public class ProductDialog extends Dialog implements
android.view.View.OnClickListener {

    public Activity c;
    public Dialog d;
    public Button close;
    public ImageView pImage;
    public TextView title;
    public TextView utensils;
    public TextView preparation;

    public ProductDialog(Activity a) {
        super(a);
        // TODO Auto-generated constructor stub
        this.c = a;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.product_dialog);
        close = (Button) findViewById(R.id.popClose);
        close.setOnClickListener(this);
        pImage = (ImageView) findViewById(R.id.popImg);
        title = (TextView) findViewById(R.id.popTitle);
        utensils = (TextView) findViewById(R.id.popUtensili);
        preparation = (TextView) findViewById(R.id.popPreparazione);

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.popClose:
            dismiss();
            break;
        default:
            break;
        }
        dismiss();
    }

    public void setImage(String urlImg) {
        Picasso.with(getContext())
          .load(urlImg)
          .placeholder(R.drawable.placeholder)
          //.transform(new RoundedTransformation(10, 0))
          .fit().centerCrop()
          .into(pImage);
    }

    public void setTitle(String txtTitle) {
        title.setText(txtTitle);
    }
    public void setUtensils(String txtUtensils) {
        utensils.setText(txtUtensils);
    }
    public void setPreparation(String txtPreparation) {
        preparation.setText(txtPreparation);
    }
}

And I call them from my Activity like this:

pDetails = new ProductDialog(MyActivity.this);
        pDetails.setTitle("asd");
        pDetails.setUtensils("asd");
        pDetails.setPreparation("asd");
        pDetails.setImage(imageUrl);
        pDetails.show();

But as soon as setTitle() gets fired I get the following error:

07-23 13:03:10.810: E/AndroidRuntime(3117): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test.test/com.test.test.MyActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

What am I missing in order to make it work?

Answer 1

You are calling those setters when views are not initialized. onCreate() method is called when show() method is called. but these setters are being called before show method. that is causing that error.

If you want to set those values from mainActivity you have to make interface to get those values or send data in constructor.

I have modified you code that can explain you how to achieve that you want. there are plenty of ways, here is the simplest one:

public Activity c;
        public Dialog d;
        public Button close;
        public ImageView pImage;
        public TextView title;
        public TextView utensils;
        public TextView preparation;

        // variables those will handle values. i did not implement it for image you can do same for that also.
        private String titleValue;
        private String utensilsValue;
        private String preparationValue;

        public ProductDialog(Activity a) {
            super(a);
            // TODO Auto-generated constructor stub 
            this.c = a;
        } 

        @Override 
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            requestWindowFeature(Window.FEATURE_NO_TITLE);
            setContentView(R.layout.product_dialog);
            close = (Button) findViewById(R.id.popClose);
            close.setOnClickListener(this);
            pImage = (ImageView) findViewById(R.id.popImg);
            title = (TextView) findViewById(R.id.popTitle);
            utensils = (TextView) findViewById(R.id.popUtensili);
            preparation = (TextView) findViewById(R.id.popPreparazione);
            title.setText(titleValue);
            utensils.setText(utensilsValue);
            preparation.setText(preparationValue);
        } 

        @Override 
        public void onClick(View v) {
            switch (v.getId()) {
            case R.id.popClose:
                dismiss();
                break; 
            default: 
                break; 
            } 
            dismiss();
        } 

        public void setImage(String urlImg) {
            Picasso.with(getContext())
              .load(urlImg)
              .placeholder(R.drawable.placeholder)
              //.transform(new RoundedTransformation(10, 0)) 
              .fit().centerCrop() 
              .into(pImage);
        } 

    // Created  getter and setter to get get value form mainActivity. 
        public void setTitle(String txtTitle) {
            titleValue = (txtTitle);
        } 
        public void setUtensils(String txtUtensils) {
            utensilsValue = (txtUtensils);
        } 
        public void setPreparation(String txtPreparation) {
            preparationValue = (txtPreparation);
        } 
    } 

Answer 2

This is because your dialog is not created. Use builder pattern to save the values before creating.