CODEWITHSUNDEEP
androiduser-interfaceandroid-custom-view
brux
brux

Reputation: 3230

CustomView extending RelativeLayout

I am trying to create a customview which will allow me to add images and text. The reason I am doing this is because in the app I am creating I am repeating the same code over and over in order to achieve this and I want to try and wrap it up into its own custom view so I can just use setters and position the view relative to one another, placing all this code in one simple to use class.

I can add text views and imageviews to the view however when I try to position them in relation to one another I always get a NPE crash.

Here is the code I have so far, it simply adds a TextView and then atempts to center the TextView inside my custom view.

public class MultiView extends RelativeLayout {
    Context cx;
    int images = 0;

    public MultiView(Context context) {

        super(context);
        cx = context;
    }

    public void addText(String textParam) {

        TextView tv = new TextView(cx);

        tv.setText(textParam);

        tv.setTextColor(Color.WHITE);

        RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) tv
                .getLayoutParams();

        layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);

//      tv.setLayoutParams(layoutParams); // the app crashes when I add this line

        this.addView(tv);
    }

}

Upvotes: 1

Views: 6182

Answers (3)

ramaral
ramaral

Reputation: 6179

Full class: 

public class MultiView extends RelativeLayout {
    Context cx;
    int images = 0;

    public MultiView(Context context) {

        super(context);
        cx = context;
    }

    public void addText(String textParam) {

        RelativeLayout.LayoutParams layoutParams = 
        new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.WRAP_CONTENT,      
            RelativeLayout.LayoutParams.WRAP_CONTENT);


        TextView tv = new TextView(cx);
        tv.setText(textParam);
        tv.setTextColor(Color.WHITE);
        layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
        tv.setLayoutParams(layoutParams);
        this.addView(tv);
    }

}

Upvotes: 2

MagicBeamer
MagicBeamer

Reputation: 256

I think you get a NPE because tv.getLayoutParams(); returns null.

Try the following :

RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);

tv.setLayoutParams(layoutParams); // the app crashes when I add this line

this.addView(tv);

Upvotes: 1

nfirex
nfirex

Reputation: 1523

It is very strange that you get crash on that line:

tv.setLayoutParams(layoutParams);

I think you that you get it on that line because created View don't have any LayoutParams (besides, if it RelativeLayout.LayoutParams):

layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);

I think that you can improve addText() method by this video from DevBytes: http://www.youtube.com/watch?v=55wLsaWpQ4g

But if you want to make your code work you need to replace your steps like this:

TextView tv = new TextView(cx);
tv.setText(textParam);
tv.setTextColor(Color.WHITE);
this.addView(tv); // Programatically created View get LayoutParams when we add it to a ViewGroup

RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) tv.getLayoutParams();
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
tv.setLayoutParams(layoutParams);

Or create your layout params by self:

TextView tv = new TextView(cx);
tv.setText(textParam);
tv.setTextColor(Color.WHITE);

RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
layoutParams.addRule(RelativeLayout.CENTER_IN_PARENT);
tv.setLayoutParams(layoutParams);

this.addView(tv);

Upvotes: 1

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