问题
I have a preference screen (responder_generic.xml) as follows:
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
<Preference
android:defaultValue="false"
android:key="auto_responder_key"
android:layout="@layout/preference_header_switch_item_responder"
android:title="@string/auto_responder">
</Preference>
</PreferenceScreen>
which i am instantiating as follows : (in version 2.3.3)
addPreferencesFromResource(R.xml.responder_generic);
and my layout = preference_header_switch_item_responder looks as follows:
<?xml version="1.0" encoding="utf-8"?>
<!-- Layout of a header item in PreferenceActivity. -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="33dp"
android:gravity="center_vertical"
android:minHeight="33dp"
android:id="@+id/preference_header_switch_item_responder"
style="?android:attr/listSeparatorTextViewStyle" >
<RelativeLayout
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_weight="1" >
<TextView
android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="marquee"
android:fadingEdge="horizontal"
android:singleLine="true"
android:text="@string/auto_responder"
android:textAppearance="?android:attr/textAppearanceSmall"
android:textStyle="bold" />
<TextView
android:id="@+id/summary"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@android:id/title"
android:ellipsize="end"
android:textAppearance="?android:attr/textAppearanceSmall" />
</RelativeLayout>
<include layout="@layout/compound_button" />
</LinearLayout>
Now, i have the compound button defined in layout folder and layout/v-14 respectively as follows :
<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" >
<CheckBox
android:id="@+id/switchWidget"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:clickable="true"
android:focusable="false"
android:padding="8dip"
android:layout_marginRight="14dip" />
</merge>
and
<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Switch
android:id="@+id/switchWidget"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:clickable="true"
android:focusable="false"
android:padding="8dip"
android:layout_marginRight="14dip"/>
</merge>
In the onPostCreate method, i am trying to find the this checkbox/switch at run time using findViewById(R.id.switchWidget) but its always returning null.
Any idea what could be the reason ?
回答1:
Reason was i was adding multiple preferences to the screen, hence, i had to resort to adding a custom preference. Detailed solution has been provided in the following link:
The solution has been provided in the following link.
usage of findviewbyid in preferenceactivity
回答2:
The reason lies in using several PreferenceScreen. Each Preference view has its own id.
To access the view IDs, you need to create your own Preference class inheriting from Preference and override onBindView
public class LogListPreference extends EditTextPreference {
public LogListPreference(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public LogListPreference(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
this.setLayoutResource(R.layout.preference_widget_loglist);
}
@Override
protected void onBindView(View view) {
super.onBindView(view);
EditText edit = (EditText) view.findViewById(R.id.logText);
...
}
}
To use your class in PreferenceScreen xml-file, specify
<PreferenceScreen
xmlns:android="http://schemas.android.com/apk/res/android">
<com.company.LogListPreference
android:title="@string/pref_log_title_log"
android:key="log_text" />
</PreferenceScreen>
Preference Layout file /layout/preference_widget_loglist.xml:
<?xml version="1.0" encoding="utf-8"?>
<!-- Layout used by CheckBoxPreference for the checkbox style. This is inflated
inside android.R.layout.preference. -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/widget_log_layout"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:minHeight="?android:attr/listPreferredItemHeight"
android:gravity="top|left"
android:orientation="vertical"
>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="?android:attr/listPreferredItemPaddingLeft"
android:paddingRight="?android:attr/listPreferredItemPaddingRight">
>
<TextView
android:id="@android:id/title"
android:textAppearance="?android:attr/textAppearanceListItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:singleLine="true"
android:ellipsize="marquee"
android:fadingEdge="horizontal" />
<TextView
android:id="@android:id/summary"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@android:id/title"
android:layout_alignStart="@android:id/title"
android:layout_below="@android:id/title"
android:maxLines="2"
android:paddingTop="6dp"
android:textAppearance="?android:attr/textAppearanceSmall"
android:textColor="?android:attr/textColorSecondary"
android:textSize="14sp" />
</RelativeLayout>
<EditText
android:id="@+id/logText"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clickable="false"
android:defaultValue="@string/pref_default_video_sources"
android:focusable="false"
android:gravity="top|left"
android:inputType="textMultiLine"
android:key="log331"
android:lines="10"
android:maxLines="2000"
android:minLines="6"
android:scrollbars="vertical"
android:scrollbarThumbVertical="?android:attr/colorBackground"
android:background="?android:attr/colorForeground"
android:textColor="?android:attr/textColorPrimaryInverse"
android:text="aaa\nbbb\nccc\naaa\nbbb"
android:title="@string/pref_title_video_sources" />
</LinearLayout>
来源：https://stackoverflow.com/questions/15708599/findviewbyid-returns-null-for-preference-layout