Setting preference layout and changing the attribute in it

问题

is it possible to access programmatically a layout which is set to a Preference?

Here is what I have, a very simple project - proof of concept

The Preference Activity:

package com.example;

import android.os.Bundle;
import android.preference.PreferenceActivity;
import android.util.Log;
import android.view.View;

public class PreferenceExampleActivity extends PreferenceActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);

        ImageView v = (ImageView) findViewById(R.id.iconka);

    }
}

The resource XML:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen
  xmlns:android="http://schemas.android.com/apk/res/android" 
  android:key="settings">
    <PreferenceCategory 
        android:title="Category Setting Name" 
        android:order="1" 
        android:key="Main">
        <Preference 
            android:order="1" 
            android:title="Setting" 
            android:summary="Setting1" 
            android:layout="@layout/profile_preference_row"
            android:key="profile" />
    </PreferenceCategory>
</PreferenceScreen>

The custom layout for the Preference:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@android:id/widget_frame"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:minHeight="?android:attr/listPreferredItemHeight"
    android:gravity="center_vertical"
    android:paddingRight="?android:attr/scrollbarSize">



    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="15dip"
        android:layout_marginRight="6dip"
        android:layout_marginTop="6dip"
        android:layout_marginBottom="6dip"
        android:layout_weight="1">

        <TextView android:id="@+android:id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:singleLine="true"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:ellipsize="marquee"
            android:fadingEdge="horizontal" />

        <TextView android:id="@+android:id/summary"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@android:id/title"
            android:layout_alignLeft="@android:id/title"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:textColor="?android:attr/textColorSecondary"
            android:maxLines="4" />

    </RelativeLayout>
    <ImageView
        android:id="@+id/iconka"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        />
</LinearLayout>

What I want is to be able to access the "iconka" ImageView from the Activity and change the image from there. I am using API 8 (Android 2.2)

Currently the "v" is null and I don't have any idea why is that.

A hint will be much appreciated!

Update - The Solution: Actually, I needed a custom preference which I can modify for my needs. This one is a practical guide how to create your own Custom preference in your project: Android & Amir - Android Preferences See the part when the author creates a custom preference class.

回答1:

Try taking a look at the following discussions on imageview. Might help you with your issue.

Android: findViewById of an ImageView (custom adapter)

Android : getting NullPointerException for ImageView imag = (ImageView) findViewById(R.id.image)

回答2:

After 20 min of hair pulling I found an elegant solution to this problem. First, extend the preference, then override the getView(View convertView, ViewGroup parent) method. My case was this: I had a preference layout with app icon and 2 text views(app name and version). I want to change app version programatically. How do I do this? just take a look below:

public class AboutUsPreference extends Preference {

    public AboutUsPreference(Context context) {
        super(context);
    }

    public AboutUsPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public AboutUsPreference(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public View getView(View convertView, ViewGroup parent) {
        View v = super.getView(convertView, parent);
        ((TextView)v.findViewById(R.id.textView2)).setText(getAppVersion());        
        return v;
    }

    private String getAppVersion(){
        PackageInfo pInfo = null;
        try {
            pInfo = getContext().getPackageManager().getPackageInfo(getContext().getPackageName(), 0);
        } catch (NameNotFoundException e) {
            Log.e(getClass().getName(), e.getMessage(), e);
            return "";
        }

        String version = pInfo.versionName;
        return getContext().getString(R.string.version, version);
    }


}

The solution is this: View v = super.getView(convertView, parent); when overriding getView method. super.getview call will return your layout view.

And my xml preference looks like:

<com.audioRec.android.settings.aboutUs.AboutUsPreference
        android:layout="@layout/about_preference_layout"/>

回答3:

try getLayoutResource to get the View of the preference and then get your ImageView

来源：https://stackoverflow.com/questions/8143838/setting-preference-layout-and-changing-the-attribute-in-it