1     final Object[] mConstructorArgs = new Object[2];
  2
  3     static final Class<?>[] mConstructorSignature = new Class[] {
  4             Context.class, AttributeSet.class};
  5
  6     //...
  7
  8     /**
  9      * Creates a view from a tag name using the supplied attribute set.
 10      * <p>
 11      * <strong>Note:</strong> Default visibility so the BridgeInflater can
 12      * override it.
 13      *
 14      * @param parent the parent view, used to inflate layout params
 15      * @param name the name of the XML tag used to define the view
 16      * @param context the inflation context for the view, typically the
 17      *                {@code parent} or base layout inflater context
 18      * @param attrs the attribute set for the XML tag used to define the view
 19      * @param ignoreThemeAttr {@code true} to ignore the {@code android:theme}
 20      *                        attribute (if set) for the view being inflated,
 21      *                        {@code false} otherwise
 22      */
 23     View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
 24             boolean ignoreThemeAttr) {
 25         //**关键1**//
 26         if (name.equals("view")) {
 27             name = attrs.getAttributeValue(null, "class");
 28         }
 29
 30         // Apply a theme wrapper, if allowed and one is specified.
 31         if (!ignoreThemeAttr) {
 32             final TypedArray ta = context.obtainStyledAttributes(attrs, ATTRS_THEME);
 33             final int themeResId = ta.getResourceId(0, 0);
 34             if (themeResId != 0) {
 35                 context = new ContextThemeWrapper(context, themeResId);
 36             }
 37             ta.recycle();
 38         }
 39
 40         if (name.equals(TAG_1995)) {
 41             // Let's party like it's 1995!
 42             return new BlinkLayout(context, attrs);
 43         }
 44
 45         try {
 46             View view;
 47             if (mFactory2 != null) {
 48                 view = mFactory2.onCreateView(parent, name, context, attrs);
 49             } else if (mFactory != null) {
 50                 view = mFactory.onCreateView(name, context, attrs);
 51             } else {
 52                 view = null;
 53             }
 54
 55             if (view == null && mPrivateFactory != null) {
 56                 view = mPrivateFactory.onCreateView(parent, name, context, attrs);
 57             }
 58
 59             if (view == null) {
 60                 final Object lastContext = mConstructorArgs[0];
 61                 mConstructorArgs[0] = context;
 62                 try {
 63                     if (-1 == name.indexOf('.')) {
 64                         //**关键2**//
 65                         view = onCreateView(parent, name, attrs);
 66                     } else {
 67                         //**关键3**//
 68                         view = createView(name, null, attrs);
 69                     }
 70                 } finally {
 71                     mConstructorArgs[0] = lastContext;
 72                 }
 73             }
 74
 75             return view;
 76         }
 77         //后面都是catch，省略
 78     }
 79
 80     protected View onCreateView(View parent, String name, AttributeSet attrs)
 81             throws ClassNotFoundException {
 82         return onCreateView(name, attrs);
 83     }
 84
 85     protected View onCreateView(String name, AttributeSet attrs)
 86             throws ClassNotFoundException {
 87         return createView(name, "android.view.", attrs);
 88     }
 89
 90     /**
 91      * Low-level function for instantiating a view by name. This attempts to
 92      * instantiate a view class of the given <var>name</var> found in this
 93      * LayoutInflater's ClassLoader.
 94      *
 95      * @param name The full name of the class to be instantiated.
 96      * @param attrs The XML attributes supplied for this instance.
 97      *
 98      * @return View The newly instantiated view, or null.
 99      */
100     public final View createView(String name, String prefix, AttributeSet attrs)
101             throws ClassNotFoundException, InflateException {
102         Constructor<? extends View> constructor = sConstructorMap.get(name);
103         Class<? extends View> clazz = null;
104
105         try {
106             Trace.traceBegin(Trace.TRACE_TAG_VIEW, name);
107
108             if (constructor == null) {
109                 //**关键4**//
110                 // Class not found in the cache, see if it's real, and try to add it
111                 clazz = mContext.getClassLoader().loadClass(
112                         prefix != null ? (prefix + name) : name).asSubclass(View.class);
113
114                 if (mFilter != null && clazz != null) {
115                     boolean allowed = mFilter.onLoadClass(clazz);
116                     if (!allowed) {
117                         failNotAllowed(name, prefix, attrs);
118                     }
119                 }
120                 constructor = clazz.getConstructor(mConstructorSignature);
121                 constructor.setAccessible(true);
122                 sConstructorMap.put(name, constructor);
123             } else {
124                 // If we have a filter, apply it to cached constructor
125                 if (mFilter != null) {
126                     // Have we seen this name before?
127                     Boolean allowedState = mFilterMap.get(name);
128                     if (allowedState == null) {
129                         // New class -- remember whether it is allowed
130                         clazz = mContext.getClassLoader().loadClass(
131                                 prefix != null ? (prefix + name) : name).asSubclass(View.class);
132
133                         boolean allowed = clazz != null && mFilter.onLoadClass(clazz);
134                         mFilterMap.put(name, allowed);
135                         if (!allowed) {
136                             failNotAllowed(name, prefix, attrs);
137                         }
138                     } else if (allowedState.equals(Boolean.FALSE)) {
139                         failNotAllowed(name, prefix, attrs);
140                     }
141                 }
142             }
143
144             Object[] args = mConstructorArgs;
145             args[1] = attrs;
146             //**关键5**//
147             final View view = constructor.newInstance(args);
148             if (view instanceof ViewStub) {
149                 // Use the same context when inflating ViewStub later.
150                 final ViewStub viewStub = (ViewStub) view;
151                 viewStub.setLayoutInflater(cloneInContext((Context) args[0]));
152             }
153             return view;
154
155         }
156         //后面都是catch以及finally处理，省略
157     }

 1 public class PhoneLayoutInflater extends LayoutInflater {
 2     private static final String[] sClassPrefixList = {
 3         "android.widget.",
 4         "android.webkit.",
 5         "android.app."
 6     };
 7     //......
 8
 9     /** Override onCreateView to instantiate names that correspond to the
10         widgets known to the Widget factory. If we don't find a match,
11         call through to our super class.
12     */
13     @Override protected View onCreateView(String name, AttributeSet attrs) throws ClassNotFoundException {
14         //**关键6**//
15         for (String prefix : sClassPrefixList) {
16             try {
17                 View view = createView(name, prefix, attrs);
18                 if (view != null) {
19                     return view;
20                 }
21             } catch (ClassNotFoundException e) {
22                 // In this case we want to let the base class take a crack
23                 // at it.
24             }
25         }
26
27         return super.onCreateView(name, attrs);
28     }
29
30     //.........
31 }

static final Class<?>[] mConstructorSignature = new Class[] {Context.class, AttributeSet.class};