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POAndroid: How to access xml resources from within an inflated custom component
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  1. POAndroid: How to access xml resources from within an inflated custom component
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    copied!<p>I'm fairly new to Android, and am trying to build a custom component in my android application. To do this, I'm extending FrameLayout, so that my custom component can consist of a spinner on top of a view (I'll eventually be drawing in the view, but it's just blank at the moment). </p> <p>Within my class that extends FrameLayout, I'd like to set up the spinner button, which I've laid out in xml. However, <strong>calling findViewById from within that class returns null.</strong> From reading answers to similar problems on here, I gather that I need to call findViewById from an activity (and indeed, if I set up the spinner from a class that extends activity, everything works fine). One solution then would be to pass an activity in to my FrameLayout class's constructor. However, I never call my FrameLayout class's constructor myself, because I use a layoutinflater to inflate it. I assume layout inflater is calling my FrameLayout class's constructor, and I'm not sure how to add an argument to its constructor call. </p> <p>Can anyone tell me what I'm doing wrong, or how I should be approaching this?</p> <p>Here's a simplified version of my code:</p> <p>My custom FrameLayout class:</p> <pre><code>package com.example.myoscilloscope.gui; import android.app.Activity; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.widget.FrameLayout; import android.widget.Spinner; import com.example.myoscilloscope.R; public class Oscilloscope extends FrameLayout { //variables private Spinner chanSelector; //the channel selector // overloading constructors public Oscilloscope(Context context) { this(context, null, 0); } public Oscilloscope(Context context, AttributeSet attrs) { this(context, attrs, 0); } public Oscilloscope(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); //set up the spinner. chanSelector = (Spinner) findViewById(R.id.channel_spinner); if(chanSelector == null){ Log.d("FROMTOM", "CHANNELSELECTOR IS NULL!"); } } } </code></pre> <p>My activity class is huge, but the oscilliscope is inflated on a button press, so the relevant section (i think) is:</p> <pre><code>import com.example.myoscilloscope.gui.Oscilloscope; // ... public void addchannel(View v){ //this initialization is actually done elsewhere, but I've copied it here // for simplicity's sake private LayoutInflater oscilloscopeInflater; LinearLayout myOscilloscopeHolder; oscilloscopeInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE); myOscilloscopeHolder = (LinearLayout)findViewById(R.id.oscilloscopeHolder); Oscilloscope myOscilliscope = (Oscilloscope)oscilloscopeInflater.inflate(R.layout.oscilloscope, myOscilloscopeHolder, false); myOscilloscopeHolder.addView(trOscilloscopes[trChannelsDisplayed]); } </code></pre> <p>Here's my Oscilloscope.xml file, which is inflated by my main program:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;com.example.myoscilloscope.gui.Oscilloscope xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/oscilloscope" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1" &gt; &lt;com.example.myoscilloscope.gui.Oscillator android:id="@+id/oscillator" android:layout_width="fill_parent" android:layout_height="fill_parent" /&gt; &lt;Spinner android:id="@+id/channel_spinner" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="bottom" /&gt; &lt;/com.example.myoscilloscope.gui.Oscilloscope&gt; </code></pre> <p>And here's the relevant bit of my main.xml:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@color/background_color" &gt; &lt;LinearLayout android:id="@id/oscilloscopeHolder" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_above="@id/rg_channels" android:layout_toLeftOf="@id/HistogramArea" android:orientation="vertical" android:background="#FFFFFF" &gt; &lt;/LinearLayout&gt; &lt;/RelativeLayout&gt; </code></pre> <p>Hopefully that makes some sense. Any insights would be much appreciated.</p> <p>Tom</p>
 

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