Utils.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mzeat.image;

import android.annotation.SuppressLint;
import android.app.ActivityManager;
import android.content.Context;
import android.graphics.Bitmap;
import android.os.Build;
import android.os.Environment;
import android.os.StatFs;
import android.widget.ImageView;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import com.mzeat.image.ImageWorker.ImageWorkerAdapter;


/**
 * Class containing some static utility methods.
 * 包含一些实用的静态方法的类
 */
public class Utils {
	public static final int IO_BUFFER_SIZE = 8 * 1024;
	private static List<String> items = null;

	private Utils() {
	};

	/**
	 * Workaround for bug pre-Froyo, see here for more info:
	 * http://android-developers.blogspot.com/2011/09/androids-http-clients.html
	 */
	public static void disableConnectionReuseIfNecessary() {
		// HTTP connection reuse which was buggy pre-froyo
		if (hasHttpConnectionBug()) {
			System.setProperty("http.keepAlive", "false");
		}
	}

	/**
	 * Get the size in bytes of a bitmap.
	 * 
	 * @param bitmap
	 * @return size in bytes
	 */
	@SuppressLint("NewApi")
	public static int getBitmapSize(Bitmap bitmap) {
		// Pre HC-MR1
		return bitmap.getRowBytes() * bitmap.getHeight();
	}

	/**
	 * Check if external storage is built-in or removable.
	 * 检查外置存储是否安装或移除
	 * @return True if external storage is removable (like an SD card), false
	 *         otherwise.
	 */
	@SuppressLint("NewApi")
	public static boolean isExternalStorageRemovable() {
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
			return Environment.isExternalStorageRemovable();
		}
		return true;
	}

	/**
	 * Get the external app cache directory.
	 * 取得外置应用缓存目录
	 * @param context
	 *            The context to use
	 * @return The external cache dir
	 */
	@SuppressLint("NewApi")
	public static File getExternalCacheDir(Context context) {
		if (hasExternalCacheDir()) {
			return context.getExternalCacheDir();
		}

		// Before Froyo we need to construct the external cache dir ourselves
		// 在2.2之前，我们需要自己建立一个外置的缓存目录
		final String cacheDir = "/Android/data/" + context.getPackageName()
				+ "/cache/";
		return new File(Environment.getExternalStorageDirectory().getPath()
				+ cacheDir);
	}

	/**
	 * Check how much usable space is available at a given path.
	 * 检查在给定路径还有多少空闲的可用空间。
	 * @param path
	 *            The path to check
	 * @return The space available in bytes
	 */
	@SuppressLint("NewApi")
	public static long getUsableSpace(File path) {
		//版本大于2.3时候，可以直接返回。
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
			return path.getUsableSpace();
		}
		//版本小于2.3的时候，需要通过计算得出。
		final StatFs stats = new StatFs(path.getPath());
		return (long) stats.getBlockSize() * (long) stats.getAvailableBlocks();
	}

	/**
	 * Get the memory class of this device (approx. per-app memory limit)
	 * 
	 * @param context
	 * @return
	 */
	public static int getMemoryClass(Context context) {
		return ((ActivityManager) context
				.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();
	}

	/**
	 * Check if OS version has a http URLConnection bug. See here for more
	 * information:
	 * http://android-developers.blogspot.com/2011/09/androids-http-clients.html
	 * 
	 * @return
	 */
	public static boolean hasHttpConnectionBug() {
		return Build.VERSION.SDK_INT < Build.VERSION_CODES.FROYO;
	}

	/**
	 * Check if OS version has built-in external cache dir method.
	 * 检查OS版本是否内置有外部缓存目录方法 版本大于2.2
	 * @return
	 */
	public static boolean hasExternalCacheDir() {
		return Build.VERSION.SDK_INT >= Build.VERSION_CODES.FROYO;
	}

	/**
	 * Check if ActionBar is available.
	 * 检查动作栏是否可用。 版本大于等于2.3
	 * @return
	 */
	public static boolean hasActionBar() {
		return Build.VERSION.SDK_INT >= 11;// Build.VERSION_CODES.HONEYCOMB;
	}

	public static ImageWorkerAdapter imageThumbWorkerUrlsAdapter = new ImageWorkerAdapter() {
		public Object getItem(int num) {
			return items.get(num);
		}

		public int getSize() {
			return items.size();
		}
	};

}