ViewUtil.java

package com.cheng.utils.view;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.content.res.Configuration;
import android.graphics.Paint;
import android.graphics.Paint.FontMetrics;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.GridView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.RelativeLayout.LayoutParams;
import android.widget.TextView;

/**
 * ViewUtils
 * <ul>
 * <strong>get view height</strong>
 * <li>{@link ViewUtil#getListViewHeightBasedOnChildren(ListView)}</li>
 * <li>{@link ViewUtil#getAbsListViewHeightBasedOnChildren(AbsListView)}</li>
 * </ul>
 * <ul>
 * <strong>set view height</strong>
 * <li>{@link ViewUtil#setViewHeight(View, int)} set view height</li>
 * <li>{@link ViewUtil#setListViewHeightBasedOnChildren(ListView)}</li>
 * <li>{@link ViewUtil#setAbsListViewHeightBasedOnChildren(AbsListView)}</li>
 * </ul>
 * <ul>
 * <strong>get other info</strong>
 * <li>{@link ViewUtil#getGridViewVerticalSpacing(GridView)} get GridView
 * vertical spacing</li>
 * </ul>
 * <ul>
 * <strong>set other info</strong>
 * <li>{@link ViewUtil#setSearchViewOnClickListener(View, OnClickListener)}</li>
 * </ul>
 */
public final class ViewUtil {

    /**
     * Don't let anyone instantiate this class.
     */
    private ViewUtil() {
        throw new Error("Do not need instantiate!");
    }

    /**
     * get ListView height according to every children
     *
     * @param view
     * @return
     */
    public static int getListViewHeightBasedOnChildren(ListView view) {
        int height = getAbsListViewHeightBasedOnChildren(view);
        ListAdapter adapter;
        int adapterCount;
        if (view != null && (adapter = view.getAdapter()) != null
                && (adapterCount = adapter.getCount()) > 0) {
            height += view.getDividerHeight() * (adapterCount - 1);
        }
        return height;
    }

    private static final String CLASS_NAME_GRID_VIEW = "android.widget.GridView";
    private static final String FIELD_NAME_VERTICAL_SPACING = "mVerticalSpacing";

    /**
     * get GridView vertical spacing
     *
     * @param view
     * @return
     */
    public static int getGridViewVerticalSpacing(GridView view) {
        // get mVerticalSpacing by android.widget.GridView
        Class<?> demo = null;
        int verticalSpacing = 0;
        try {
            demo = Class.forName(CLASS_NAME_GRID_VIEW);
            Field field = demo.getDeclaredField(FIELD_NAME_VERTICAL_SPACING);
            field.setAccessible(true);
            verticalSpacing = (Integer) field.get(view);
            return verticalSpacing;
        } catch (Exception e) {
            /**
             * accept all exception, include ClassNotFoundException,
             * NoSuchFieldException, InstantiationException,
             * IllegalArgumentException, IllegalAccessException,
             * NullPointException
             */
            e.printStackTrace();
        }
        return verticalSpacing;
    }

    /**
     * get AbsListView height according to every children
     *
     * @param view
     * @return
     */
    public static int getAbsListViewHeightBasedOnChildren(AbsListView view) {
        ListAdapter adapter;
        if (view == null || (adapter = view.getAdapter()) == null) {
            return 0;
        }

        int height = 0;
        for (int i = 0; i < adapter.getCount(); i++) {
            View item = adapter.getView(i, null, view);
            if (item instanceof ViewGroup) {
                item.setLayoutParams(new LayoutParams(
                        LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
            }
            item.measure(0, 0);
            height += item.getMeasuredHeight();
        }
        height += view.getPaddingTop() + view.getPaddingBottom();
        return height;
    }

    /**
     * get Font height
     *
     * @param view
     * @return
     */
    public static int getFontHeight(TextView view) {
        Paint paint = new Paint();
        paint.setTextSize(view.getTextSize());
        FontMetrics fm = paint.getFontMetrics();
        return (int) (Math.ceil(fm.descent - fm.ascent));
    }

    /**
     * set view height
     *
     * @param view
     * @param height
     */
    public static void setViewHeight(View view, int height) {
        if (view == null) {
            return;
        }

        ViewGroup.LayoutParams params = view.getLayoutParams();
        params.height = height;
    }

    // /**
    // * set GistView height which is calculated by {@link #
    // getGridViewHeightBasedOnChildren(GridView)}
    // *
    // * @param view
    // * @return
    // */
    // public static void setGridViewHeightBasedOnChildren(GridView view) {
    // setViewHeight(view, getGridViewHeightBasedOnChildren(view));
    // }

    /**
     * set ListView height which is calculated by
     * {@link # getListViewHeightBasedOnChildren(ListView)}
     *
     * @param view
     * @return
     */
    public static void setListViewHeightBasedOnChildren(ListView view) {
        setViewHeight(view, getListViewHeightBasedOnChildren(view));
    }

    /**
     * set AbsListView height which is calculated by
     * {@link # getAbsListViewHeightBasedOnChildren(AbsListView)}
     *
     * @param view
     * @return
     */
    public static void setAbsListViewHeightBasedOnChildren(AbsListView view) {
        setViewHeight(view, getAbsListViewHeightBasedOnChildren(view));
    }

    /**
     * set SearchView OnClickListener
     *
     * @param v
     * @param listener
     */
    public static void setSearchViewOnClickListener(View v,
                                                    OnClickListener listener) {
        if (v instanceof ViewGroup) {
            ViewGroup group = (ViewGroup) v;
            int count = group.getChildCount();
            for (int i = 0; i < count; i++) {
                View child = group.getChildAt(i);
                if (child instanceof LinearLayout
                        || child instanceof RelativeLayout) {
                    setSearchViewOnClickListener(child, listener);
                }

                if (child instanceof TextView) {
                    TextView text = (TextView) child;
                    text.setFocusable(false);
                }
                child.setOnClickListener(listener);
            }
        }
    }

    /**
     * get descended views from parent.
     *
     * @param parent
     * @param filter          Type of views which will be returned.
     * @param includeSubClass Whether returned list will include views which are subclass of
     *                        filter or not.
     * @return
     */
    public static <T extends View> List<T> getDescendants(ViewGroup parent,
                                                          Class<T> filter, boolean includeSubClass) {
        List<T> descendedViewList = new ArrayList<T>();
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            Class<? extends View> childsClass = child.getClass();
            if ((includeSubClass && filter.isAssignableFrom(childsClass))
                    || (!includeSubClass && childsClass == filter)) {
                descendedViewList.add(filter.cast(child));
            }
            if (child instanceof ViewGroup) {
                descendedViewList.addAll(getDescendants((ViewGroup) child,
                        filter, includeSubClass));
            }
        }
        return descendedViewList;
    }

    /**
     * Helps determine if the app is running in a Tablet context.
     *
     * @param context
     * @return
     */
    public static boolean isTablet(Context context) {
        return (context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_LARGE;
    }

}