Your activity (and your list-view) is not yet visible in the onStart.
Don't use 'getChildCount' and 'getChildAt' method to check your
preference-settings.
BTW: If your activity is not yet visible, how can a user make a
selection?
Shouldn't you query in the onPause, for example.
And also, the positions returned by the method getCheckedItemPositions
() are the positions in your adapter (ArrayAdapter in your case). Your
list-*view* positions (used in getChildAt) are not the same. You list-
view will never have more children than the ones you can see. And the
child-at postion 0 is the one on the top of the list-view.
On Oct 7, 2:37 pm, KhanAzul <mark.pes...@gmail.com> wrote:
> I want to display a ListView with checkboxes, and I want some of the
> checkboxes pre-selected. The ListView has setAdapter called during
> onCreate, and the list information appears when the screen is drawn.
> However, when I attempt to set certain list items as checked, my
> ListView reports getChildCount() = 0.
>
> My SharedPreferences contains a list of sounds that have been
> previously selected, as a comma delimited string of list indices.
> Because the list appears to have no children in onStart, my attempts
> to set items as checked fails.
>
> On the good side, once the list is rendered, I can select entries and
> hit Back, and my selection is stored to SharedPreferences correctly.
>
> How can I load my previous selection into the list? Should I be using
> something else here?
>
> In the spirit of open source, here's my code, free to you :)
>
> ====================================================
> SoundLibrary.Java
> ====================================================
>
> import java.util.Hashtable;
>
> import android.app.Activity;
> import android.content.Context;
> import android.content.SharedPreferences;
> import android.content.res.Resources;
> import android.media.MediaPlayer;
> import android.os.Bundle;
> import android.util.SparseBooleanArray;
> import android.view.View;
> import android.view.View.OnLongClickListener;
> import android.widget.ArrayAdapter;
> import android.widget.ListView;
>
> public class SoundLibrary extends Activity{
> ListView lstSounds;
> Hashtable<String, Integer> soundTable;
> CharSequence[] soundNames;
> CharSequence[] soundLocations;
> OnLongClickListener previewListener;
> static Context myContext;
> static MediaPlayer player;
> SharedPreferences prefs;
>
> @Override
> public void onCreate(Bundle savedInstanceState) {
> super.onCreate(savedInstanceState);
> setContentView(R.layout.soundlibrary);
> myContext = this.getApplicationContext();
> prefs = getSharedPreferences("myAppData", 0);
>
> soundTable = new Hashtable<String, Integer>();
> LoadSoundTable();
> lstSounds = (ListView)findViewById(R.id.lstSounds);
> PopulateSoundList();
> lstSounds.setOnLongClickListener(new PreviewListener());
> }
>
> @Override
> public void onStart() {
> super.onStart();
> String[] selectedSoundsArray =
> prefs.getString("selectedSounds", "").split(",");
> for (int selI = 0; selI < selectedSoundsArray.length; selI++)
> {
> if (lstSounds.getChildCount() <= selI) {
> break;
> }
> try {
>
> lstSounds.getChildAt(Integer.parseInt(selectedSoundsArray
> [selI])).setSelected(true);
> } catch (NumberFormatException e) { }
> }
> }
>
> @Override
> public void onPause() {
> super.onPause();
> StringBuffer sb = new StringBuffer();
> SparseBooleanArray sbaSelectedSounds =
> lstSounds.getCheckedItemPositions();
> for (int sbaKey = 0; sbaKey < sbaSelectedSounds.size();
> sbaKey++)
> {
> if (sbaSelectedSounds.get(sbaKey, false))
> {
> sb.append(String.valueOf(sbaKey));
> sb.append(',');
> }
> }
> prefs.edit().putString("selectedSounds",
> sb.toString()).commit();
> }
>
> private void LoadSoundTable()
> {
> Resources res = getResources();
> CharSequence[] soundNames =
> res.getTextArray(R.array.sound_name);
> CharSequence[] soundLocations =
> res.getTextArray(R.array.sound_location);
>
> for (int i = 0; i < soundNames.length; i++) {
> soundTable.put(soundNames[i].toString(),
>
> res.getIdentifier(soundLocations[i].toString(), "raw",
> this.getPackageName()));
> }
> }
>
> private void PopulateSoundList()
> {
> ArrayAdapter<String> aa = new ArrayAdapter<String>(this,
> android.R.layout.simple_list_item_multiple_choice,
> soundTable.keySet().toArray(new
> String[soundTable.keySet
> ().size()]));
> lstSounds.setAdapter(aa);
> }
>
> private class PreviewListener extends Activity implements
> OnLongClickListener {
> public boolean onLongClick(View v) {
> String previewSoundName =
> lstSounds.getSelectedItem().toString();
> player = MediaPlayer.create(myContext,
>
> soundTable.get(previewSoundName).intValue());
> player.start();
> return true;
> }
> }
>
> }
>
> ====================================================
> soundlibrary.xml - in res/layout
> ====================================================
>
> <?xml version="1.0" encoding="utf-8"?>
> <LinearLayout
> xmlns:android="http://schemas.android.com/apk/res/android";
> android:layout_width="fill_parent"
> android:layout_height="wrap_content"
> android:gravity="center"
> android:orientation="vertical">
>
> <TextView
> android:layout_width="wrap_content"
> android:layout_height="wrap_content"
> android:id="@+id/txtTitle"
> android:text="@string/sound_library_title"></TextView>
>
> <ListView
> android:id="@+id/lstSounds"
> android:layout_width="fill_parent"
> android:layout_height="fill_parent"
> android:choiceMode="multipleChoice"
> android:clickable="true"
> android:focusable="true"
> android:longClickable="true"></ListView>
>
> <TextView
> android:layout_width="wrap_content"
> android:layout_height="wrap_content"
> android:id="@+id/txtPreview"
> android:text="@string/sound_library_preview"></TextView>
>
> </LinearLayout>
>
> ====================================================
> sounds.xml - in res/values
> ====================================================
> <?xml version="1.0" encoding="utf-8"?>
> <resources>
> <string-array name="sound_name">
> <item>Big Sound</item>
> <item>Little Sound</item>
> </string-array>
> <string-array name="sound_location">
> <item>test_big_sound</item>
> <item>test_little_sound</item>
> </string-array>
> </resources>
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