Java tutorial
/* * Copyright (C) 2012 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.sb.tododemo.widgets; import android.content.Context; import android.content.res.TypedArray; import android.os.Bundle; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentTransaction; import android.util.AttributeSet; import android.view.View; import android.view.ViewGroup; import android.widget.FrameLayout; import android.widget.LinearLayout; import android.widget.TabHost; import android.widget.TabWidget; import java.util.ArrayList; /** * Special TabHost that allows the use of {@link Fragment} objects for its tab * content. When placing this in a view hierarchy, after inflating the hierarchy * you must call {@link #setup(Context, FragmentManager, int)} to complete the * initialization of the tab host. Customized to allow saving fragment states * when switching between tabs. Any fragment placed in this tabhost that needs * to maintain it's state when switching tabs needs to implement * {@linkplain Saveable} */ public class SavedStateFragmentTabHost extends TabHost implements TabHost.OnTabChangeListener { private static final String TAG = "SavedStateFragmentTabHost"; private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>(); private FrameLayout mRealTabContent; private Context mContext; private FragmentManager mFragmentManager; private int mContainerId; private TabHost.OnTabChangeListener mOnTabChangeListener; private TabInfo mLastTab; private boolean mAttached; static final class TabInfo { private final String tag; private final Class<?> clss; private final Bundle args; private Bundle stateArgs; private Fragment fragment; TabInfo(final String _tag, final Class<?> _class, final Bundle _args) { tag = _tag; clss = _class; args = _args; } } static class DummyTabFactory implements TabHost.TabContentFactory { private final Context mContext; public DummyTabFactory(final Context context) { mContext = context; } @Override public View createTabContent(final String tag) { final View v = new View(mContext); v.setMinimumWidth(0); v.setMinimumHeight(0); return v; } } static class SavedState extends BaseSavedState { String curTab; SavedState(final Parcelable superState) { super(superState); } private SavedState(final Parcel in) { super(in); curTab = in.readString(); } @Override public void writeToParcel(final Parcel out, final int flags) { super.writeToParcel(out, flags); out.writeString(curTab); } @Override public String toString() { return "SavedStateFragmentTabHost.SavedState{" + Integer.toHexString(System.identityHashCode(this)) + " curTab=" + curTab + "}"; } /** * IMPORTANT: Do not rename or change the scope of this field as it is * part of {@link Parcelable}'s Contract */ public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() { @Override public SavedState createFromParcel(final Parcel in) { return new SavedState(in); } @Override public SavedState[] newArray(final int size) { return new SavedState[size]; } }; } public SavedStateFragmentTabHost(final Context context) { // Note that we call through to the version that takes an AttributeSet, // because the simple Context construct can result in a broken object! super(context, null); initFragmentTabHost(context, null); } public SavedStateFragmentTabHost(final Context context, final AttributeSet attrs) { super(context, attrs); initFragmentTabHost(context, attrs); } private void initFragmentTabHost(final Context context, final AttributeSet attrs) { final TypedArray a = context.obtainStyledAttributes(attrs, new int[] { android.R.attr.inflatedId }, 0, 0); mContainerId = a.getResourceId(0, 0); a.recycle(); super.setOnTabChangedListener(this); // If owner hasn't made its own view hierarchy, then as a convenience // we will construct a standard one here. if (findViewById(android.R.id.tabs) == null) { final LinearLayout ll = new LinearLayout(context); ll.setOrientation(LinearLayout.VERTICAL); addView(ll, new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)); final TabWidget tw = new TabWidget(context); tw.setId(android.R.id.tabs); tw.setOrientation(LinearLayout.HORIZONTAL); ll.addView(tw, new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT, 0)); FrameLayout fl = new FrameLayout(context); fl.setId(android.R.id.tabcontent); ll.addView(fl, new LinearLayout.LayoutParams(0, 0, 0)); mRealTabContent = fl = new FrameLayout(context); mRealTabContent.setId(mContainerId); ll.addView(fl, new LinearLayout.LayoutParams(android.view.ViewGroup.LayoutParams.MATCH_PARENT, 0, 1)); } } /** * @deprecated Don't call the original TabHost setup, you must instead call * {@link #setup(Context, FragmentManager)} or * {@link #setup(Context, FragmentManager, int)}. */ @Override @Deprecated public void setup() { throw new IllegalStateException("Must call setup() that takes a Context and FragmentManager"); } public void setup(final Context context, final FragmentManager manager) { super.setup(); mContext = context; mFragmentManager = manager; ensureContent(); } public void setup(final Context context, final FragmentManager manager, final int containerId) { super.setup(); mContext = context; mFragmentManager = manager; mContainerId = containerId; ensureContent(); mRealTabContent.setId(containerId); // We must have an ID to be able to save/restore our state. If // the owner hasn't set one at this point, we will set it ourself. if (getId() == View.NO_ID) { setId(android.R.id.tabhost); } } private void ensureContent() { if (mRealTabContent == null) { mRealTabContent = (FrameLayout) findViewById(mContainerId); if (mRealTabContent == null) { throw new IllegalStateException("No tab content FrameLayout found for id " + mContainerId); } } } @Override public void setOnTabChangedListener(final OnTabChangeListener l) { mOnTabChangeListener = l; } public void addTab(final TabHost.TabSpec tabSpec, final Class<?> clss, final Bundle args) { tabSpec.setContent(new DummyTabFactory(mContext)); final String tag = tabSpec.getTag(); final TabInfo info = new TabInfo(tag, clss, args); if (mAttached) { // If we are already attached to the window, then check to make // sure this tab's fragment is inactive if it exists. This shouldn't // normally happen. info.fragment = mFragmentManager.findFragmentByTag(tag); if ((info.fragment != null) && !info.fragment.isDetached()) { final FragmentTransaction ft = mFragmentManager.beginTransaction(); ft.detach(info.fragment); ft.commit(); } } mTabs.add(info); addTab(tabSpec); } @Override protected void onAttachedToWindow() { super.onAttachedToWindow(); final String currentTab = getCurrentTabTag(); // Go through all tabs and make sure their fragments match // the correct state. FragmentTransaction ft = null; for (int i = 0; i < mTabs.size(); i++) { final TabInfo tab = mTabs.get(i); tab.fragment = mFragmentManager.findFragmentByTag(tab.tag); if ((tab.fragment != null) && !tab.fragment.isDetached()) { if (tab.tag.equals(currentTab)) { // The fragment for this tab is already there and // active, and it is what we really want to have // as the current tab. Nothing to do. mLastTab = tab; } else { // This fragment was restored in the active state, // but is not the current tab. Deactivate it. if (ft == null) { ft = mFragmentManager.beginTransaction(); } ft.detach(tab.fragment); } } } // We are now ready to go. Make sure we are switched to the // correct tab. mAttached = true; ft = doTabChanged(currentTab, ft); if (ft != null) { // TODO // 07-29 16:36:26.084: E/AndroidRuntime(20047): // java.lang.IllegalStateException: Can not perform this action // after onSaveInstanceState ft.commit(); mFragmentManager.executePendingTransactions(); } } @Override protected void onDetachedFromWindow() { super.onDetachedFromWindow(); mAttached = false; } @Override protected Parcelable onSaveInstanceState() { final Parcelable superState = super.onSaveInstanceState(); final SavedState ss = new SavedState(superState); ss.curTab = getCurrentTabTag(); return ss; } @Override protected void onRestoreInstanceState(final Parcelable state) { final SavedState ss = (SavedState) state; super.onRestoreInstanceState(ss.getSuperState()); setCurrentTabByTag(ss.curTab); } @Override public void onTabChanged(final String tabId) { if (mAttached) { final FragmentTransaction ft = doTabChanged(tabId, null); if (ft != null) { ft.commit(); // TODO // 07-29 16:36:26.084: E/AndroidRuntime(20047): // java.lang.IllegalStateException: Can not perform this action // after onSaveInstanceState } } if (mOnTabChangeListener != null) { mOnTabChangeListener.onTabChanged(tabId); } } private FragmentTransaction doTabChanged(final String tabId, final FragmentTransaction fragmenTrans) { FragmentTransaction ft = fragmenTrans; TabInfo newTab = null; for (int i = 0; i < mTabs.size(); i++) { final TabInfo tab = mTabs.get(i); if (tab.tag.equals(tabId)) { newTab = tab; } } if (newTab == null) { throw new IllegalStateException("No tab known for tag " + tabId); } if (mLastTab != newTab) { if (ft == null) { ft = mFragmentManager.beginTransaction(); } if ((mLastTab != null) && (mLastTab.fragment != null)) { if (mLastTab.fragment instanceof Saveable) { if (mLastTab.stateArgs == null) { mLastTab.stateArgs = new Bundle(); } ((Saveable) mLastTab.fragment).saveState(mLastTab.stateArgs); } ft.detach(mLastTab.fragment); } if (newTab.fragment == null) { newTab.fragment = Fragment.instantiate(mContext, newTab.clss.getName(), newTab.args); ft.add(mContainerId, newTab.fragment, newTab.tag); } else { if (newTab.fragment instanceof Saveable) { ((Saveable) newTab.fragment).restoreState(newTab.stateArgs); } ft.attach(newTab.fragment); } mLastTab = newTab; } return ft; } public static interface Saveable { public void saveState(Bundle state); public void restoreState(Bundle state); } }