src/com/xtremelabs/droidsugar/view/ViewLoader.java

package com.xtremelabs.droidsugar.view;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import java.io.File;
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ViewLoader extends XmlLoader {
    private Map<String, ViewNode> viewNodesByLayoutName = new HashMap<String, ViewNode>();

    public ViewLoader(ResourceExtractor resourceExtractor) {
        super(resourceExtractor);
    }

    @Override
    protected void processResourceXml(File xmlFile, Document document) throws Exception {
        ViewNode topLevelNode = new ViewNode("top-level", new HashMap<String, String>());
        processChildren(document.getChildNodes(), topLevelNode);
        viewNodesByLayoutName.put(
                "layout/" + xmlFile.getName().replace(".xml", ""),
                topLevelNode.getChildren().get(0));
    }

    private void processChildren(NodeList childNodes, ViewNode parent) {
        for (int i = 0; i < childNodes.getLength(); i++) {
            Node node = childNodes.item(i);
            processNode(node, parent);
        }
    }

    private void processNode(Node node, ViewNode parent) {
        String name = node.getNodeName();
        NamedNodeMap attributes = node.getAttributes();
        Map<String, String> attrMap = new HashMap<String, String>();
        if (attributes != null) {
            int length = attributes.getLength();
            for (int i = 0; i < length; i++) {
                Node attr = attributes.item(i);
                attrMap.put(attr.getNodeName(), attr.getNodeValue());
            }
        }

        if (!name.startsWith("#")) {
            ViewNode viewNode = new ViewNode(name, attrMap);
            if (parent != null) parent.addChild(viewNode);

            String idAttr = getIdAttr(node);
            if (idAttr != null && idAttr.startsWith("@+id/")) {
                idAttr = idAttr.substring(5);

                Integer id = resourceExtractor.getResourceStringToId().get("id/" + idAttr);
                if (id == null) {
                    throw new RuntimeException("unknown id " + getIdAttr(node));
                }
                viewNode.setId(id);
            }

            processChildren(node.getChildNodes(), viewNode);
        }
    }

    public View inflateView(Context context, String key) {
        ViewNode viewNode = viewNodesByLayoutName.get(key);
        if (viewNode == null) {
            throw new RuntimeException("no such layout " + key);
        }
        try {
            return viewNode.inflate(context);
        } catch (Exception e) {
            throw new RuntimeException("error inflating " + key, e);
        }
    }

    public View inflateView(Context context, int resourceId) {
        return inflateView(context, resourceExtractor.getResourceName(resourceId));
    }

    private class ViewNode {
        private String name;
        private final Map<String, String> attributes;

        private List<ViewNode> children = new ArrayList<ViewNode>();
        private Integer id;

        public ViewNode(String name, Map<String, String> attributes) {
            this.name = name;
            this.attributes = attributes;
        }

        public List<ViewNode> getChildren() {
            return children;
        }

        public void addChild(ViewNode viewNode) {
            children.add(viewNode);
        }

        public View inflate(Context context) throws Exception {
            View view = create(context);
            if (id != null && view.getId() == 0) {
                view.setId(id);
            }
            for (ViewNode child : children) {
                ((ViewGroup) view).addView(child.inflate(context));
            }
            return view;
        }

        private View create(Context context) throws Exception {
            if (name.equals("include")) {
                String layout = attributes.get("layout");
                return inflateView(context, layout.substring(1));
            } else if (name.equals("merge")) {
                return new LinearLayout(context);
            } else {
                Class<? extends View> clazz = loadClass(name);
                if (clazz == null) {
                    clazz = loadClass("android.view." + name);
                }
                if (clazz == null) {
                    clazz = loadClass("android.widget." + name);
                }
                if (clazz == null) {
                    clazz = loadClass("com.google.android.maps." + name);
                }

                if (clazz == null) {
                    throw new RuntimeException("couldn't find view class " + name);
                }
                Constructor<? extends View> constructor;
                try {
                    constructor = clazz.getConstructor(Context.class);
                    return constructor.newInstance(context);
                } catch (NoSuchMethodException e) {
                    constructor = clazz.getConstructor(Context.class, String.class);
                    return constructor.newInstance(context, "");
                }
            }
        }

        private Class<? extends View> loadClass(String className) {
            try {
                //noinspection unchecked
                return (Class<? extends View>) getClass().getClassLoader().loadClass(className);
            } catch (ClassNotFoundException e) {
                return null;
            }
        }

        public void setId(Integer id) {
            this.id = id;
        }
    }
}