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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.app;
     18 
     19 import com.android.ide.common.rendering.api.IProjectCallback;
     20 import com.android.tools.layoutlib.annotations.LayoutlibDelegate;
     21 
     22 import android.content.Context;
     23 import android.os.Bundle;
     24 
     25 /**
     26  * Delegate used to provide new implementation of a select few methods of {@link Fragment}
     27  *
     28  * Through the layoutlib_create tool, the original  methods of Fragment have been replaced
     29  * by calls to methods of the same name in this delegate class.
     30  *
     31  * The methods being re-implemented are the ones responsible for instantiating Fragment objects.
     32  * Because the classes of these objects are found in the project, these methods need access to
     33  * {@link IProjectCallback} object. They are however static methods, so the callback is set
     34  * before the inflation through {@link #setProjectCallback(IProjectCallback)}.
     35  */
     36 public class Fragment_Delegate {
     37 
     38     private static IProjectCallback sProjectCallback;
     39 
     40     /**
     41      * Sets the current {@link IProjectCallback} to be used to instantiate classes coming
     42      * from the project being rendered.
     43      */
     44     public static void setProjectCallback(IProjectCallback projectCallback) {
     45         sProjectCallback = projectCallback;
     46     }
     47 
     48     /**
     49      * Like {@link #instantiate(Context, String, Bundle)} but with a null
     50      * argument Bundle.
     51      */
     52     @LayoutlibDelegate
     53     /*package*/ static Fragment instantiate(Context context, String fname) {
     54         return instantiate(context, fname, null);
     55     }
     56 
     57     /**
     58      * Create a new instance of a Fragment with the given class name.  This is
     59      * the same as calling its empty constructor.
     60      *
     61      * @param context The calling context being used to instantiate the fragment.
     62      * This is currently just used to get its ClassLoader.
     63      * @param fname The class name of the fragment to instantiate.
     64      * @param args Bundle of arguments to supply to the fragment, which it
     65      * can retrieve with {@link #getArguments()}.  May be null.
     66      * @return Returns a new fragment instance.
     67      * @throws InstantiationException If there is a failure in instantiating
     68      * the given fragment class.  This is a runtime exception; it is not
     69      * normally expected to happen.
     70      */
     71     @LayoutlibDelegate
     72     /*package*/ static Fragment instantiate(Context context, String fname, Bundle args) {
     73         try {
     74             if (sProjectCallback != null) {
     75                 Fragment f = (Fragment) sProjectCallback.loadView(fname,
     76                         new Class[0], new Object[0]);
     77 
     78                 if (args != null) {
     79                     args.setClassLoader(f.getClass().getClassLoader());
     80                     f.mArguments = args;
     81                 }
     82                 return f;
     83             }
     84 
     85             return null;
     86         } catch (ClassNotFoundException e) {
     87             throw new Fragment.InstantiationException("Unable to instantiate fragment " + fname
     88                     + ": make sure class name exists, is public, and has an"
     89                     + " empty constructor that is public", e);
     90         } catch (java.lang.InstantiationException e) {
     91             throw new Fragment.InstantiationException("Unable to instantiate fragment " + fname
     92                     + ": make sure class name exists, is public, and has an"
     93                     + " empty constructor that is public", e);
     94         } catch (IllegalAccessException e) {
     95             throw new Fragment.InstantiationException("Unable to instantiate fragment " + fname
     96                     + ": make sure class name exists, is public, and has an"
     97                     + " empty constructor that is public", e);
     98         } catch (Exception e) {
     99             throw new Fragment.InstantiationException("Unable to instantiate fragment " + fname
    100                     + ": make sure class name exists, is public, and has an"
    101                     + " empty constructor that is public", e);
    102         }
    103     }
    104 }
    105