Java tutorial
/* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.preference; import android.annotation.UnsupportedAppUsage; import android.app.Dialog; import android.content.Context; import android.content.DialogInterface; import android.content.res.TypedArray; import android.graphics.drawable.Drawable; import android.os.Bundle; import android.os.Parcel; import android.os.Parcelable; import android.text.TextUtils; import android.util.AttributeSet; import android.view.LayoutInflater; import android.view.View; import android.view.Window; import android.widget.Adapter; import android.widget.AdapterView; import android.widget.ListAdapter; import android.widget.ListView; import android.widget.TextView; /** * Represents a top-level {@link Preference} that * is the root of a Preference hierarchy. A {@link PreferenceActivity} * points to an instance of this class to show the preferences. To instantiate * this class, use {@link PreferenceManager#createPreferenceScreen(Context)}. * <ul> * This class can appear in two places: * <li> When a {@link PreferenceActivity} points to this, it is used as the root * and is not shown (only the contained preferences are shown). * <li> When it appears inside another preference hierarchy, it is shown and * serves as the gateway to another screen of preferences (either by showing * another screen of preferences as a {@link Dialog} or via a * {@link Context#startActivity(android.content.Intent)} from the * {@link Preference#getIntent()}). The children of this {@link PreferenceScreen} * are NOT shown in the screen that this {@link PreferenceScreen} is shown in. * Instead, a separate screen will be shown when this preference is clicked. * </ul> * <p>Here's an example XML layout of a PreferenceScreen:</p> * <pre> <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:key="first_preferencescreen"> <CheckBoxPreference android:key="wifi enabled" android:title="WiFi" /> <PreferenceScreen android:key="second_preferencescreen" android:title="WiFi settings"> <CheckBoxPreference android:key="prefer wifi" android:title="Prefer WiFi" /> ... other preferences here ... </PreferenceScreen> </PreferenceScreen> </pre> * <p> * In this example, the "first_preferencescreen" will be used as the root of the * hierarchy and given to a {@link PreferenceActivity}. The first screen will * show preferences "WiFi" (which can be used to quickly enable/disable WiFi) * and "WiFi settings". The "WiFi settings" is the "second_preferencescreen" and when * clicked will show another screen of preferences such as "Prefer WiFi" (and * the other preferences that are children of the "second_preferencescreen" tag). * * <div class="special reference"> * <h3>Developer Guides</h3> * <p>For information about building a settings UI with Preferences, * read the <a href="{@docRoot}guide/topics/ui/settings.html">Settings</a> * guide.</p> * </div> * * @see PreferenceCategory */ public final class PreferenceScreen extends PreferenceGroup implements AdapterView.OnItemClickListener, DialogInterface.OnDismissListener { @UnsupportedAppUsage private ListAdapter mRootAdapter; private Dialog mDialog; @UnsupportedAppUsage private ListView mListView; private int mLayoutResId = com.android.internal.R.layout.preference_list_fragment; private Drawable mDividerDrawable; private boolean mDividerSpecified; /** * Do NOT use this constructor, use {@link PreferenceManager#createPreferenceScreen(Context)}. * @hide- */ @UnsupportedAppUsage public PreferenceScreen(Context context, AttributeSet attrs) { super(context, attrs, com.android.internal.R.attr.preferenceScreenStyle); TypedArray a = context.obtainStyledAttributes(null, com.android.internal.R.styleable.PreferenceScreen, com.android.internal.R.attr.preferenceScreenStyle, 0); mLayoutResId = a.getResourceId(com.android.internal.R.styleable.PreferenceScreen_screenLayout, mLayoutResId); if (a.hasValueOrEmpty(com.android.internal.R.styleable.PreferenceScreen_divider)) { mDividerDrawable = a.getDrawable(com.android.internal.R.styleable.PreferenceScreen_divider); mDividerSpecified = true; } a.recycle(); } /** * Returns an adapter that can be attached to a {@link PreferenceActivity} * or {@link PreferenceFragment} to show the preferences contained in this * {@link PreferenceScreen}. * <p> * This {@link PreferenceScreen} will NOT appear in the returned adapter, instead * it appears in the hierarchy above this {@link PreferenceScreen}. * <p> * This adapter's {@link Adapter#getItem(int)} should always return a * subclass of {@link Preference}. * * @return An adapter that provides the {@link Preference} contained in this * {@link PreferenceScreen}. */ public ListAdapter getRootAdapter() { if (mRootAdapter == null) { mRootAdapter = onCreateRootAdapter(); } return mRootAdapter; } /** * Creates the root adapter. * * @return An adapter that contains the preferences contained in this {@link PreferenceScreen}. * @see #getRootAdapter() */ protected ListAdapter onCreateRootAdapter() { return new PreferenceGroupAdapter(this); } /** * Binds a {@link ListView} to the preferences contained in this {@link PreferenceScreen} via * {@link #getRootAdapter()}. It also handles passing list item clicks to the corresponding * {@link Preference} contained by this {@link PreferenceScreen}. * * @param listView The list view to attach to. */ public void bind(ListView listView) { listView.setOnItemClickListener(this); listView.setAdapter(getRootAdapter()); onAttachedToActivity(); } @Override protected void onClick() { if (getIntent() != null || getFragment() != null || getPreferenceCount() == 0) { return; } showDialog(null); } private void showDialog(Bundle state) { Context context = getContext(); if (mListView != null) { mListView.setAdapter(null); } LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); View childPrefScreen = inflater.inflate(mLayoutResId, null); View titleView = childPrefScreen.findViewById(android.R.id.title); mListView = (ListView) childPrefScreen.findViewById(android.R.id.list); if (mDividerSpecified) { mListView.setDivider(mDividerDrawable); } bind(mListView); // Set the title bar if title is available, else no title bar final CharSequence title = getTitle(); Dialog dialog = mDialog = new Dialog(context, context.getThemeResId()); if (TextUtils.isEmpty(title)) { if (titleView != null) { titleView.setVisibility(View.GONE); } dialog.getWindow().requestFeature(Window.FEATURE_NO_TITLE); } else { if (titleView instanceof TextView) { ((TextView) titleView).setText(title); titleView.setVisibility(View.VISIBLE); } else { dialog.setTitle(title); } } dialog.setContentView(childPrefScreen); dialog.setOnDismissListener(this); if (state != null) { dialog.onRestoreInstanceState(state); } // Add the screen to the list of preferences screens opened as dialogs getPreferenceManager().addPreferencesScreen(dialog); dialog.show(); } public void onDismiss(DialogInterface dialog) { mDialog = null; getPreferenceManager().removePreferencesScreen(dialog); } /** * Used to get a handle to the dialog. * This is useful for cases where we want to manipulate the dialog * as we would with any other activity or view. */ public Dialog getDialog() { return mDialog; } public void onItemClick(AdapterView parent, View view, int position, long id) { // If the list has headers, subtract them from the index. if (parent instanceof ListView) { position -= ((ListView) parent).getHeaderViewsCount(); } Object item = getRootAdapter().getItem(position); if (!(item instanceof Preference)) return; final Preference preference = (Preference) item; preference.performClick(this); } @Override protected boolean isOnSameScreenAsChildren() { return false; } @Override protected Parcelable onSaveInstanceState() { final Parcelable superState = super.onSaveInstanceState(); final Dialog dialog = mDialog; if (dialog == null || !dialog.isShowing()) { return superState; } final SavedState myState = new SavedState(superState); myState.isDialogShowing = true; myState.dialogBundle = dialog.onSaveInstanceState(); return myState; } @Override protected void onRestoreInstanceState(Parcelable state) { if (state == null || !state.getClass().equals(SavedState.class)) { // Didn't save state for us in onSaveInstanceState super.onRestoreInstanceState(state); return; } SavedState myState = (SavedState) state; super.onRestoreInstanceState(myState.getSuperState()); if (myState.isDialogShowing) { showDialog(myState.dialogBundle); } } private static class SavedState extends BaseSavedState { boolean isDialogShowing; Bundle dialogBundle; public SavedState(Parcel source) { super(source); isDialogShowing = source.readInt() == 1; dialogBundle = source.readBundle(); } @Override public void writeToParcel(Parcel dest, int flags) { super.writeToParcel(dest, flags); dest.writeInt(isDialogShowing ? 1 : 0); dest.writeBundle(dialogBundle); } public SavedState(Parcelable superState) { super(superState); } public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() { public SavedState createFromParcel(Parcel in) { return new SavedState(in); } public SavedState[] newArray(int size) { return new SavedState[size]; } }; } }