android ui helper对象防止活动被GC

Question

Is it a bad idea to create a UIHelper class that takes an activity reference? I'm trying to understand and avoid memory leaks and one of the biggest problems I've read is to not pass around contexts. I have this UIHelper class that takes a reference to an activity and builds/returns TextView and EditView objects to my activity. I'm thinking this is keeping my activities from being GC'ed but i'm not sure. Is there a more appropriate way of doing this?

Here is my UIHelper class

public class UIHelper {

    private Activity activity;
    private LinearLayout.LayoutParams inputParms = new LinearLayout.LayoutParams(
            LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    private LinearLayout.LayoutParams labelParms = new LinearLayout.LayoutParams(
            LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    private LinearLayout.LayoutParams valueParms = new LinearLayout.LayoutParams(
            LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    private static String[] USStates;

    public UIHelper(Activity activity){
        this.activity = activity;
        this.USStates = activity.getResources().getStringArray(R.array.USStates);

        labelParms.setMargins(5, 5, 0, 0);
        inputParms.setMargins(5, 2, 0, 12);
    }

    public View buildEditView(RecordItem recordItem){
        String type = recordItem.getType();

        if(type.equalsIgnoreCase("text") || type.equalsIgnoreCase("phone") || type.equalsIgnoreCase("integer")){

            EditText vTextInput = new EditText(activity);
            vTextInput.setTextSize(20);
            vTextInput.setLayoutParams(inputParms);

            if (type.equalsIgnoreCase("integer")) {
                vTextInput.setInputType(InputType.TYPE_CLASS_NUMBER);
            } else if (type.equalsIgnoreCase("phone")) {
                vTextInput.setInputType(InputType.TYPE_CLASS_PHONE);
            }

            if (!recordItem.getDisplay()) {
                vTextInput.setVisibility(View.GONE);
            }

            vTextInput.setSingleLine();
            recordItem.setEditView(vTextInput);

            return vTextInput;

        }else if(type.equalsIgnoreCase("USState")){

            Spinner vSpinnerInput = new Spinner(activity);
            ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(
                    activity,
                    android.R.layout.simple_spinner_item, USStates);
            dataAdapter
                    .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            vSpinnerInput.setAdapter(dataAdapter);
            recordItem.setEditView(vSpinnerInput);

            return vSpinnerInput;
        }else if(type.equalsIgnoreCase("keyword")){

            Spinner vSpinnerInput = new Spinner(activity);
            recordItem.setEditView(vSpinnerInput);

            return vSpinnerInput;
        }else if(type.equalsIgnoreCase("recordPicker")){
            TextView textView = new TextView(activity);

            textView.setTextSize(20);
            textView.setGravity(Gravity.LEFT);
            valueParms.topMargin = 17;
            textView.setLayoutParams(valueParms);
            //textView.setBackgroundColor(0xFFC2EAFF);
            textView.setBackgroundColor(0xFFFFFFD0);
            textView.setPadding(15, 7, 0, 7);

            recordItem.setEditView(textView);
            return textView;
        } 

        Log.i("C2_UIHelper", "returned a null editView!");
        return null;
    }

    public TextView buildLabelView(RecordItem recordItem){
        TextView vLabel = new TextView(activity);
        vLabel.setText(recordItem.getLabel());
        vLabel.setTextSize(12);
        vLabel.setLayoutParams(labelParms);
        vLabel.setTextColor(0xFF777777);
        return vLabel;
    }
}

Answer 1

You can do this, and sometimes it cleans up your code. The important thing is that when the activity's onDestroy is called, you need to call a cleanup method on the helper that sets the variable holding the context to null, so you don't keep a circular reference between the two variables.

Answer 2

As long as you only keep a reference to your UIHelper inside the Activity, there should be no problem. In that case it will be GCed together with the Activity. You only run into problems if you keep references around in places that hang around longer, eg in static variables, ThreadLocals or fields in your Application class and Services.