Java tutorial
/* * Copyright (C) 2010 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 com.achep.base.ui.fragments; import android.content.Intent; import android.os.Bundle; import android.os.Message; import android.preference.Preference; import android.preference.PreferenceManager; import android.preference.PreferenceScreen; import android.support.annotation.NonNull; import android.support.v4.app.Fragment; import android.view.KeyEvent; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ListView; import com.achep.acdisplay.R; import com.achep.base.async.WeakHandler; import com.achep.base.ui.fragments.leakcanary.LeakWatchFragment; import com.achep.base.utils.PreferenceManagerUtils; import java.lang.reflect.Method; /** * Shows a hierarchy of {@link android.preference.Preference} objects as * lists. These preferences will * automatically save to {@link android.content.SharedPreferences} as the user interacts with * them. To retrieve an instance of {@link android.content.SharedPreferences} that the * preference hierarchy in this fragment will use, call * {@link android.preference.PreferenceManager#getDefaultSharedPreferences(android.content.Context)} * with a context in the same package as this fragment. * <p> * Furthermore, the preferences shown will follow the visual style of system * preferences. It is easy to create a hierarchy of preferences (that can be * shown on multiple screens) via XML. For these reasons, it is recommended to * use this fragment (as a superclass) to deal with preferences in applications. * <p> * A {@link android.preference.PreferenceScreen} object should be at the top of the preference * hierarchy. Furthermore, subsequent {@link android.preference.PreferenceScreen} in the hierarchy * denote a screen break--that is the preferences contained within subsequent * {@link android.preference.PreferenceScreen} should be shown on another screen. The preference * framework handles showing these other screens from the preference hierarchy. * <p> * The preference hierarchy can be formed in multiple ways: * <li> From an XML file specifying the hierarchy * <li> From different {@link android.app.Activity Activities} that each specify its own * preferences in an XML file via {@link android.app.Activity} meta-data * <li> From an object hierarchy rooted with {@link android.preference.PreferenceScreen} * <p> * To inflate from XML, use the {@link #addPreferencesFromResource(int)}. The * root element should be a {@link android.preference.PreferenceScreen}. Subsequent elements can point * to actual {@link android.preference.Preference} subclasses. As mentioned above, subsequent * {@link android.preference.PreferenceScreen} in the hierarchy will result in the screen break. * <p> * To specify an {@link android.content.Intent} to query {@link android.app.Activity Activities} that each * have preferences, use {@link #addPreferencesFromIntent}. Each * {@link android.app.Activity} can specify meta-data in the manifest (via the key * {@link android.preference.PreferenceManager#METADATA_KEY_PREFERENCES}) that points to an XML * resource. These XML resources will be inflated into a single preference * hierarchy and shown by this fragment. * <p> * To specify an object hierarchy rooted with {@link android.preference.PreferenceScreen}, use * {@link #setPreferenceScreen(android.preference.PreferenceScreen)}. * <p> * As a convenience, this fragment implements a click listener for any * preference in the current hierarchy, see * {@link #onPreferenceTreeClick(android.preference.PreferenceScreen, android.preference.Preference)}. * <p/> * <div class="special reference"> * <h3>Developer Guides</h3> * <p>For information about using {@code PreferenceFragment}, * read the <a href="{@docRoot}guide/topics/ui/settings.html">Settings</a> * guide.</p> * </div> * <p/> * <a name="SampleCode"></a> * <h3>Sample Code</h3> * <p/> * <p>The following sample code shows a simple preference fragment that is * populated from a resource. The resource it loads is:</p> * <p/> * {@sample development/samples/ApiDemos/res/xml/preferences.xml preferences} * <p/> * <p>The fragment implementation itself simply populates the preferences * when created. Note that the preferences framework takes care of loading * the current values out of the app preferences and writing them when changed:</p> * <p/> * {@sample development/samples/ApiDemos/src/com/example/android/apis/preference/FragmentPreferences.java * fragment} * * @see android.preference.Preference * @see android.preference.PreferenceScreen */ public abstract class PreferenceFragmentBase extends LeakWatchFragment implements PreferenceManagerUtils.OnPreferenceTreeClickListener { private static final String PREFERENCES_TAG = "android:preferences"; private PreferenceManager mPreferenceManager; private ListView mList; private boolean mHavePrefs; private boolean mInitDone; /** * The starting request code given out to preference framework. */ private static final int FIRST_REQUEST_CODE = 100; private static final int MSG_BIND_PREFERENCES = 1; private final H mHandler = new H(this); private static class H extends WeakHandler<PreferenceFragmentBase> { public H(@NonNull PreferenceFragmentBase object) { super(object); } @Override protected void onHandleMassage(@NonNull PreferenceFragmentBase pfb, Message msg) { switch (msg.what) { case MSG_BIND_PREFERENCES: pfb.bindPreferences(); break; } } } final private Runnable mRequestFocus = new Runnable() { public void run() { mList.focusableViewAvailable(mList); } }; /** * Interface that PreferenceFragment's containing activity should * implement to be able to process preference items that wish to * switch to a new fragment. */ public interface OnPreferenceStartFragmentCallback { /** * Called when the user has clicked on a Preference that has * a fragment class name associated with it. The implementation * to should instantiate and switch to an instance of the given * fragment. */ boolean onPreferenceStartFragment(PreferenceFragmentBase caller, Preference pref); } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mPreferenceManager = PreferenceManagerUtils.newInstance(getActivity(), FIRST_REQUEST_CODE); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.preference_list_fragment, container, false); } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); if (mHavePrefs) { bindPreferences(); } mInitDone = true; if (savedInstanceState != null) { Bundle container = savedInstanceState.getBundle(PREFERENCES_TAG); if (container != null) { final PreferenceScreen preferenceScreen = getPreferenceScreen(); if (preferenceScreen != null) { preferenceScreen.restoreHierarchyState(container); } } } } @Override public void onStart() { super.onStart(); PreferenceManagerUtils.setOnPreferenceTreeClickListener(mPreferenceManager, this); } @Override public void onStop() { super.onStop(); PreferenceManagerUtils.dispatchActivityStop(mPreferenceManager); PreferenceManagerUtils.setOnPreferenceTreeClickListener(mPreferenceManager, null); } @Override public void onDestroyView() { mList = null; mHandler.removeCallbacks(mRequestFocus); mHandler.removeMessages(MSG_BIND_PREFERENCES); super.onDestroyView(); } @Override public void onDestroy() { super.onDestroy(); PreferenceManagerUtils.dispatchActivityDestroy(mPreferenceManager); } @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); final PreferenceScreen preferenceScreen = getPreferenceScreen(); if (preferenceScreen != null) { Bundle container = new Bundle(); preferenceScreen.saveHierarchyState(container); outState.putBundle(PREFERENCES_TAG, container); } } @Override public void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); PreferenceManagerUtils.dispatchActivityResult(mPreferenceManager, requestCode, resultCode, data); } /** * Returns the {@link android.preference.PreferenceManager} used by this fragment. * * @return The {@link android.preference.PreferenceManager}. */ public PreferenceManager getPreferenceManager() { return mPreferenceManager; } /** * Sets the root of the preference hierarchy that this fragment is showing. * * @param preferenceScreen The root {@link android.preference.PreferenceScreen} of the preference hierarchy. */ public void setPreferenceScreen(PreferenceScreen preferenceScreen) { boolean r = PreferenceManagerUtils.setPreferences(mPreferenceManager, preferenceScreen); if (r && preferenceScreen != null) { onUnbindPreferences(); mHavePrefs = true; if (mInitDone) { postBindPreferences(); } } } /** * Gets the root of the preference hierarchy that this fragment is showing. * * @return The {@link android.preference.PreferenceScreen} that is the root of the preference * hierarchy. */ public PreferenceScreen getPreferenceScreen() { return PreferenceManagerUtils.getPreferenceScreen(mPreferenceManager); } /** * Adds preferences from activities that match the given {@link android.content.Intent}. * * @param intent The {@link android.content.Intent} to query activities. */ public void addPreferencesFromIntent(Intent intent) { requirePreferenceManager(); setPreferenceScreen( PreferenceManagerUtils.inflateFromIntent(mPreferenceManager, intent, getPreferenceScreen())); } /** * Inflates the given XML resource and adds the preference hierarchy to the current * preference hierarchy. * * @param preferencesResId The XML resource ID to inflate. */ public void addPreferencesFromResource(int preferencesResId) { requirePreferenceManager(); setPreferenceScreen(PreferenceManagerUtils.inflateFromResource(mPreferenceManager, getActivity(), preferencesResId, getPreferenceScreen())); } /** * {@inheritDoc} */ public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) { return preference.getFragment() != null && getActivity() instanceof PreferenceFragmentBase.OnPreferenceStartFragmentCallback && ((PreferenceFragmentBase.OnPreferenceStartFragmentCallback) getActivity()) .onPreferenceStartFragment(this, preference); } /** * Finds a {@link android.preference.Preference} based on its key. * * @param key The key of the preference to retrieve. * @return The {@link android.preference.Preference} with the key, or null. * @see android.preference.PreferenceGroup#findPreference(CharSequence) */ public Preference findPreference(CharSequence key) { if (mPreferenceManager == null) { return null; } return mPreferenceManager.findPreference(key); } private void requirePreferenceManager() { if (mPreferenceManager == null) { throw new RuntimeException("This should be called after super.onCreate."); } } private void postBindPreferences() { if (mHandler.hasMessages(MSG_BIND_PREFERENCES)) return; mHandler.obtainMessage(MSG_BIND_PREFERENCES).sendToTarget(); } private void bindPreferences() { final PreferenceScreen preferenceScreen = getPreferenceScreen(); if (preferenceScreen != null) { preferenceScreen.bind(getListView()); } onBindPreferences(); } protected void onBindPreferences() { } protected void onUnbindPreferences() { } public ListView getListView() { ensureList(); return mList; } private void ensureList() { if (mList != null) { return; } View root = getView(); if (root == null) { throw new IllegalStateException("Content view not yet created"); } View rawListView = root.findViewById(android.R.id.list); if (!(rawListView instanceof ListView)) { throw new RuntimeException( "Content has view with id attribute 'android.R.id.list' " + "that is not a ListView class"); } mList = (ListView) rawListView; mList.setOnKeyListener(mListOnKeyListener); mHandler.post(mRequestFocus); } private final View.OnKeyListener mListOnKeyListener = new View.OnKeyListener() { @Override public boolean onKey(View v, int keyCode, KeyEvent event) { Object selectedItem = mList.getSelectedItem(); if (selectedItem instanceof Preference) { View selectedView = mList.getSelectedView(); Preference pref = (Preference) selectedItem; try { Method method = pref.getClass().getDeclaredMethod("onKey", View.class, int.class, KeyEvent.class); method.setAccessible(true); return (boolean) method.invoke(pref, selectedView, keyCode, event); } catch (Exception ignored) { /* unused*/ } } return false; } }; }