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LayoutInflater.javaAPI DocAndroid 1.5 API30880Wed May 06 22:41:56 BST 2009android.view

LayoutInflater

public abstract class LayoutInflater extends Object
This class is used to instantiate layout XML file into its corresponding View objects. It is never be used directly -- use {@link android.app.Activity#getLayoutInflater()} or {@link Context#getSystemService} to retrieve a standard LayoutInflater instance that is already hooked up to the current context and correctly configured for the device you are running on. For example: 
LayoutInflater inflater = (LayoutInflater)context.getSystemService
Context.LAYOUT_INFLATER_SERVICE);

To create a new LayoutInflater with an additional {@link Factory} for your own views, you can use {@link #cloneInContext} to clone an existing ViewFactory, and then call {@link #setFactory} on it to include your Factory.

For performance reasons, view inflation relies heavily on pre-processing of XML files that is done at build time. Therefore, it is not currently possible to use LayoutInflater with an XmlPullParser over a plain XML file at runtime; it only works with an XmlPullParser returned from a compiled resource (R.something file.)

see
Context#getSystemService

Fields Summary
private final boolean
DEBUG
protected final android.content.Context
mContext
This field should be made private, so it is hidden from the SDK. {@hide}
private boolean
mFactorySet
private Factory
mFactory
private Filter
mFilter
private final Object[]
mConstructorArgs
private static final Class[]
mConstructorSignature
private static final HashMap
sConstructorMap
private HashMap
mFilterMap
private static final String
TAG_MERGE
private static final String
TAG_INCLUDE
private static final String
TAG_REQUEST_FOCUS
Constructors Summary
protected LayoutInflater(android.content.Context context)
Create a new LayoutInflater instance associated with a particular Context. Applications will almost always want to use {@link Context#getSystemService Context.getSystemService()} to retrieve the standard {@link Context#LAYOUT_INFLATER_SERVICE Context.INFLATER_SERVICE}.

param
context The Context in which this LayoutInflater will create its Views; most importantly, this supplies the theme from which the default values for their attributes are retrieved.

        mContext = context;
protected LayoutInflater(LayoutInflater original, android.content.Context newContext)
Create a new LayoutInflater instance that is a copy of an existing LayoutInflater, optionally with its Context changed. For use in implementing {@link #cloneInContext}.

param
original The original LayoutInflater to copy.
param
newContext The new Context to use.

        mContext = newContext;
        mFactory = original.mFactory;
        mFilter = original.mFilter;
Methods Summary
public abstract android.view.LayoutInflatercloneInContext(android.content.Context newContext)
Create a copy of the existing LayoutInflater object, with the copy pointing to a different Context than the original. This is used by {@link ContextThemeWrapper} to create a new LayoutInflater to go along with the new Context theme.

param
newContext The new Context to associate with the new LayoutInflater. May be the same as the original Context if desired.
return
Returns a brand spanking new LayoutInflater object associated with the given Context.

public final ViewcreateView(java.lang.String name, java.lang.String prefix, android.util.AttributeSet attrs)
Low-level function for instantiating a view by name. This attempts to
instantiate a view class of the given name found in this
LayoutInflater's ClassLoader.



There are two things that can happen in an error case: either the
exception describing the error will be thrown, or a null will be
returned. You must deal with both possibilities -- the former will happen
the first time createView() is called for a class of a particular name,
the latter every time there-after for that class name.
param
name The full name of the class to be instantiated.
param
attrs The XML attributes supplied for this instance.
return
View The newly instantied view, or null.
        Constructor constructor = sConstructorMap.get(name);

        try {
            if (constructor == null) {
                // Class not found in the cache, see if it's real, and try to add it
                Class clazz = mContext.getClassLoader().loadClass(
                        prefix != null ? (prefix + name) : name);
                
                if (mFilter != null && clazz != null) {
                    boolean allowed = mFilter.onLoadClass(clazz);
                    if (!allowed) {
                        failNotAllowed(name, prefix, attrs);
                    }
                }
                constructor = clazz.getConstructor(mConstructorSignature);
                sConstructorMap.put(name, constructor);
            } else {
                // If we have a filter, apply it to cached constructor
                if (mFilter != null) {
                    // Have we seen this name before?
                    Boolean allowedState = mFilterMap.get(name);
                    if (allowedState == null) {
                        // New class -- remember whether it is allowed
                        Class clazz = mContext.getClassLoader().loadClass(
                                prefix != null ? (prefix + name) : name);
                        
                        boolean allowed = clazz != null && mFilter.onLoadClass(clazz);
                        mFilterMap.put(name, allowed);
                        if (!allowed) {
                            failNotAllowed(name, prefix, attrs);
                        }
                    } else if (allowedState.equals(Boolean.FALSE)) {
                        failNotAllowed(name, prefix, attrs);
                    }
                }
            }

            Object[] args = mConstructorArgs;
            args[1] = attrs;
            return (View) constructor.newInstance(args);

        } catch (NoSuchMethodException e) {
            InflateException ie = new InflateException(attrs.getPositionDescription()
                    + ": Error inflating class "
                    + (prefix != null ? (prefix + name) : name));
            ie.initCause(e);
            throw ie;

        } catch (ClassNotFoundException e) {
            // If loadClass fails, we should propagate the exception.
            throw e;
        } catch (Exception e) {
            InflateException ie = new InflateException(attrs.getPositionDescription()
                    + ": Error inflating class "
                    + (constructor == null ? "<unknown>" : constructor.getClass().getName()));
            ie.initCause(e);
            throw ie;
        }
    
ViewcreateViewFromTag(java.lang.String name, android.util.AttributeSet attrs)
        if (name.equals("view")) {
            name = attrs.getAttributeValue(null, "class");
        }

        if (DEBUG) System.out.println("******** Creating view: " + name);

        try {
            View view = (mFactory == null) ? null : mFactory.onCreateView(name,
                    mContext, attrs);

            if (view == null) {
                if (-1 == name.indexOf('.")) {
                    view = onCreateView(name, attrs);
                } else {
                    view = createView(name, null, attrs);
                }
            }

            if (DEBUG) System.out.println("Created view is: " + view);
            return view;

        } catch (InflateException e) {
            throw e;

        } catch (ClassNotFoundException e) {
            InflateException ie = new InflateException(attrs.getPositionDescription()
                    + ": Error inflating class " + name);
            ie.initCause(e);
            throw ie;

        } catch (Exception e) {
            InflateException ie = new InflateException(attrs.getPositionDescription()
                    + ": Error inflating class " + name);
            ie.initCause(e);
            throw ie;
        }
    
private voidfailNotAllowed(java.lang.String name, java.lang.String prefix, android.util.AttributeSet attrs)
Throw an excpetion because the specified class is not allowed to be inflated.
        InflateException ie = new InflateException(attrs.getPositionDescription()
                + ": Class not allowed to be inflated "
                + (prefix != null ? (prefix + name) : name));
        throw ie;
    
public static android.view.LayoutInflaterfrom(android.content.Context context)
Obtains the LayoutInflater from the given context.
        LayoutInflater LayoutInflater =
                (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (LayoutInflater == null) {
            throw new AssertionError("LayoutInflater not found.");
        }
        return LayoutInflater;
    
public android.content.ContextgetContext()
Return the context we are running in, for access to resources, class
loader, etc.
        return mContext;
    
public final android.view.LayoutInflater$FactorygetFactory()
Return the current factory (or null). This is called on each element
name. If the factory returns a View, add that to the hierarchy. If it
returns null, proceed to call onCreateView(name).
        return mFactory;
    
public android.view.LayoutInflater$FiltergetFilter()
return
The {@link Filter} currently used by this LayoutInflater to restrict the set of Views
that are allowed to be inflated.
        return mFilter;
    
public Viewinflate(int resource, ViewGroup root)
Inflate a new view hierarchy from the specified xml resource. Throws
{@link InflateException} if there is an error.
param
resource ID for an XML layout resource to load (e.g.,
R.layout.main_page)
param
root Optional view to be the parent of the generated hierarchy.
return
The root View of the inflated hierarchy. If root was supplied,
this is the root View; otherwise it is the root of the inflated
XML file.
        return inflate(resource, root, root != null);
    
public Viewinflate(org.xmlpull.v1.XmlPullParser parser, ViewGroup root)
Inflate a new view hierarchy from the specified xml node. Throws
{@link InflateException} if there is an error. *


Important   For performance
reasons, view inflation relies heavily on pre-processing of XML files
that is done at build time. Therefore, it is not currently possible to
use LayoutInflater with an XmlPullParser over a plain XML file at runtime.
param
parser XML dom node containing the description of the view
hierarchy.
param
root Optional view to be the parent of the generated hierarchy.
return
The root View of the inflated hierarchy. If root was supplied,
this is the root View; otherwise it is the root of the inflated
XML file.
        return inflate(parser, root, root != null);
    
public Viewinflate(int resource, ViewGroup root, boolean attachToRoot)
Inflate a new view hierarchy from the specified xml resource. Throws
{@link InflateException} if there is an error.
param
resource ID for an XML layout resource to load (e.g.,
R.layout.main_page)
param
root Optional view to be the parent of the generated hierarchy (if
attachToRoot is true), or else simply an object that
provides a set of LayoutParams values for root of the returned
hierarchy (if attachToRoot is false.)
param
attachToRoot Whether the inflated hierarchy should be attached to
the root parameter? If false, root is only used to create the
correct subclass of LayoutParams for the root view in the XML.
return
The root View of the inflated hierarchy. If root was supplied and
attachToRoot is true, this is root; otherwise it is the root of
the inflated XML file.
        if (DEBUG) System.out.println("INFLATING from resource: " + resource);
        XmlResourceParser parser = getContext().getResources().getLayout(resource);
        try {
            return inflate(parser, root, attachToRoot);
        } finally {
            parser.close();
        }
    
public Viewinflate(org.xmlpull.v1.XmlPullParser parser, ViewGroup root, boolean attachToRoot)
Inflate a new view hierarchy from the specified XML node. Throws
{@link InflateException} if there is an error.


Important   For performance
reasons, view inflation relies heavily on pre-processing of XML files
that is done at build time. Therefore, it is not currently possible to
use LayoutInflater with an XmlPullParser over a plain XML file at runtime.
param
parser XML dom node containing the description of the view
hierarchy.
param
root Optional view to be the parent of the generated hierarchy (if
attachToRoot is true), or else simply an object that
provides a set of LayoutParams values for root of the returned
hierarchy (if attachToRoot is false.)
param
attachToRoot Whether the inflated hierarchy should be attached to
the root parameter? If false, root is only used to create the
correct subclass of LayoutParams for the root view in the XML.
return
The root View of the inflated hierarchy. If root was supplied and
attachToRoot is true, this is root; otherwise it is the root of
the inflated XML file.
        synchronized (mConstructorArgs) {
            final AttributeSet attrs = Xml.asAttributeSet(parser);
            mConstructorArgs[0] = mContext;
            View result = root;

            try {
                // Look for the root node.
                int type;
                while ((type = parser.next()) != XmlPullParser.START_TAG &&
                        type != XmlPullParser.END_DOCUMENT) {
                    // Empty
                }

                if (type != XmlPullParser.START_TAG) {
                    throw new InflateException(parser.getPositionDescription()
                            + ": No start tag found!");
                }

                final String name = parser.getName();
                
                if (DEBUG) {
                    System.out.println("**************************");
                    System.out.println("Creating root view: "
                            + name);
                    System.out.println("**************************");
                }

                if (TAG_MERGE.equals(name)) {
                    if (root == null || !attachToRoot) {
                        throw new InflateException("<merge /> can be used only with a valid "
                                + "ViewGroup root and attachToRoot=true");
                    }

                    rInflate(parser, root, attrs);
                } else {
                    // Temp is the root view that was found in the xml
                    View temp = createViewFromTag(name, attrs);

                    ViewGroup.LayoutParams params = null;

                    if (root != null) {
                        if (DEBUG) {
                            System.out.println("Creating params from root: " +
                                    root);
                        }
                        // Create layout params that match root, if supplied
                        params = root.generateLayoutParams(attrs);
                        if (!attachToRoot) {
                            // Set the layout params for temp if we are not
                            // attaching. (If we are, we use addView, below)
                            temp.setLayoutParams(params);
                        }
                    }

                    if (DEBUG) {
                        System.out.println("-----> start inflating children");
                    }
                    // Inflate all children under temp
                    rInflate(parser, temp, attrs);
                    if (DEBUG) {
                        System.out.println("-----> done inflating children");
                    }

                    // We are supposed to attach all the views we found (int temp)
                    // to root. Do that now.
                    if (root != null && attachToRoot) {
                        root.addView(temp, params);
                    }

                    // Decide whether to return the root that was passed in or the
                    // top view found in xml.
                    if (root == null || !attachToRoot) {
                        result = temp;
                    }
                }

            } catch (XmlPullParserException e) {
                InflateException ex = new InflateException(e.getMessage());
                ex.initCause(e);
                throw ex;
            } catch (IOException e) {
                InflateException ex = new InflateException(
                        parser.getPositionDescription()
                        + ": " + e.getMessage());
                ex.initCause(e);
                throw ex;
            }

            return result;
        }
    
protected ViewonCreateView(java.lang.String name, android.util.AttributeSet attrs)
This routine is responsible for creating the correct subclass of View
given the xml element name. Override it to handle custom view objects. If
you override this in your subclass be sure to call through to
super.onCreateView(name) for names you do not recognize.
param
name The fully qualified class name of the View to be create.
param
attrs An AttributeSet of attributes to apply to the View.
return
View The View created.
        return createView(name, "android.view.", attrs);
    
private voidparseInclude(org.xmlpull.v1.XmlPullParser parser, View parent, android.util.AttributeSet attrs)

        int type;

        if (parent instanceof ViewGroup) {
            final int layout = attrs.getAttributeResourceValue(null, "layout", 0);
            if (layout == 0) {
                final String value = attrs.getAttributeValue(null, "layout");
                if (value == null) {
                    throw new InflateException("You must specifiy a layout in the"
                            + " include tag: <include layout=\"@layout/layoutID\" />");
                } else {
                    throw new InflateException("You must specifiy a valid layout "
                            + "reference. The layout ID " + value + " is not valid.");
                }
            } else {
                final XmlResourceParser childParser =
                        getContext().getResources().getLayout(layout);

                try {
                    final AttributeSet childAttrs = Xml.asAttributeSet(childParser);

                    while ((type = childParser.next()) != XmlPullParser.START_TAG &&
                            type != XmlPullParser.END_DOCUMENT) {
                        // Empty.
                    }

                    if (type != XmlPullParser.START_TAG) {
                        throw new InflateException(childParser.getPositionDescription() +
                                ": No start tag found!");
                    }

                    final String childName = childParser.getName();

                    if (TAG_MERGE.equals(childName)) {
                        // Inflate all children.
                        rInflate(childParser, parent, childAttrs);
                    } else {
                        final View view = createViewFromTag(childName, childAttrs);
                        final ViewGroup group = (ViewGroup) parent;

                        // We try to load the layout params set in the <include /> tag. If
                        // they don't exist, we will rely on the layout params set in the
                        // included XML file.
                        // During a layoutparams generation, a runtime exception is thrown
                        // if either layout_width or layout_height is missing. We catch
                        // this exception and set localParams accordingly: true means we
                        // successfully loaded layout params from the <include /> tag,
                        // false means we need to rely on the included layout params.
                        ViewGroup.LayoutParams params = null;
                        try {
                            params = group.generateLayoutParams(attrs);
                        } catch (RuntimeException e) {
                            params = group.generateLayoutParams(childAttrs);
                        } finally {
                            if (params != null) {
                                view.setLayoutParams(params);
                            }
                        }

                        // Inflate all children.
                        rInflate(childParser, view, childAttrs);

                        // Attempt to override the included layout's android:id with the
                        // one set on the <include /> tag itself.
                        TypedArray a = mContext.obtainStyledAttributes(attrs,
                            com.android.internal.R.styleable.View, 0, 0);
                        int id = a.getResourceId(com.android.internal.R.styleable.View_id, View.NO_ID);
                        // While we're at it, let's try to override android:visibility.
                        int visibility = a.getInt(com.android.internal.R.styleable.View_visibility, -1);
                        a.recycle();

                        if (id != View.NO_ID) {
                            view.setId(id);
                        }

                        switch (visibility) {
                            case 0:
                                view.setVisibility(View.VISIBLE);
                                break;
                            case 1:
                                view.setVisibility(View.INVISIBLE);
                                break;
                            case 2:
                                view.setVisibility(View.GONE);
                                break;
                        }

                        group.addView(view);
                    }
                } finally {
                    childParser.close();
                }
            }
        } else {
            throw new InflateException("<include /> can only be used inside of a ViewGroup");
        }

        final int currentDepth = parser.getDepth();
        while (((type = parser.next()) != XmlPullParser.END_TAG ||
                parser.getDepth() > currentDepth) && type != XmlPullParser.END_DOCUMENT) {
            // Empty
        }
    
private voidparseRequestFocus(org.xmlpull.v1.XmlPullParser parser, View parent)
        int type;
        parent.requestFocus();
        final int currentDepth = parser.getDepth();
        while (((type = parser.next()) != XmlPullParser.END_TAG ||
                parser.getDepth() > currentDepth) && type != XmlPullParser.END_DOCUMENT) {
            // Empty
        }
    
private voidrInflate(org.xmlpull.v1.XmlPullParser parser, View parent, android.util.AttributeSet attrs)
Recursive method used to descend down the xml hierarchy and instantiate
views, instantiate their children, and then call onFinishInflate().

        final int depth = parser.getDepth();
        int type;

        while (((type = parser.next()) != XmlPullParser.END_TAG ||
                parser.getDepth() > depth) && type != XmlPullParser.END_DOCUMENT) {

            if (type != XmlPullParser.START_TAG) {
                continue;
            }

            final String name = parser.getName();
            
            if (TAG_REQUEST_FOCUS.equals(name)) {
                parseRequestFocus(parser, parent);
            } else if (TAG_INCLUDE.equals(name)) {
                if (parser.getDepth() == 0) {
                    throw new InflateException("<include /> cannot be the root element");
                }
                parseInclude(parser, parent, attrs);
            } else if (TAG_MERGE.equals(name)) {
                throw new InflateException("<merge /> must be the root element");
            } else {
                final View view = createViewFromTag(name, attrs);
                final ViewGroup viewGroup = (ViewGroup) parent;
                final ViewGroup.LayoutParams params = viewGroup.generateLayoutParams(attrs);
                rInflate(parser, view, attrs);
                viewGroup.addView(view, params);
            }
        }

        parent.onFinishInflate();
    
public voidsetFactory(android.view.LayoutInflater$Factory factory)
Attach a custom Factory interface for creating views while using
this LayoutInflater. This must not be null, and can only be set once;
after setting, you can not change the factory. This is
called on each element name as the xml is parsed. If the factory returns
a View, that is added to the hierarchy. If it returns null, the next
factory default {@link #onCreateView} method is called.


If you have an existing
LayoutInflater and want to add your own factory to it, use
{@link #cloneInContext} to clone the existing instance and then you
can use this function (once) on the returned new instance. This will
merge your own factory with whatever factory the original instance is
using.
        if (mFactorySet) {
            throw new IllegalStateException("A factory has already been set on this LayoutInflater");
        }
        if (factory == null) {
            throw new NullPointerException("Given factory can not be null");
        }
        mFactorySet = true;
        if (mFactory == null) {
            mFactory = factory;
        } else {
            mFactory = new FactoryMerger(factory, mFactory);
        }
    
public voidsetFilter(android.view.LayoutInflater$Filter filter)
Sets the {@link Filter} to by this LayoutInflater. If a view is attempted to be inflated
which is not allowed by the {@link Filter}, the {@link #inflate(int, ViewGroup)} call will
throw an {@link InflateException}. This filter will replace any previous filter set on this
LayoutInflater.
param
filter The Filter which restricts the set of Views that are allowed to be inflated.
This filter will replace any previous filter set on this LayoutInflater.
        mFilter = filter;
        if (filter != null) {
            mFilterMap = new HashMap<String, Boolean>();
        }