android 实用工具类-手机存储

最新推荐文章于 2024-09-23 15:49:23 发布

hhlin1

最新推荐文章于 2024-09-23 15:49:23 发布

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分类专栏： android

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本文提供了一种应用程序缓存目录管理的方法，通过检测外部存储状态和权限，智能选择最佳的缓存路径。支持SD卡及设备文件系统的缓存管理。

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import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Environment;

import java.io.File;
import java.io.IOException;

import static android.os.Environment.MEDIA_MOUNTED;

/**
 * Provides application storage paths
 *
 * @author Sergey Tarasevich (nostra13[at]gmail[dot]com)
 * @since 1.0.0
 */
public final class StorageUtils {

	private static final String EXTERNAL_STORAGE_PERMISSION = "android.permission.WRITE_EXTERNAL_STORAGE";
	private static final String INDIVIDUAL_DIR_NAME = "uil-images";

	private StorageUtils() {
	}

	/**
	 * Returns application cache directory. Cache directory will be created on SD card
	 * <i>("/Android/data/[app_package_name]/cache")</i> if card is mounted and app has appropriate permission. Else -
	 * Android defines cache directory on device's file system.
	 *
	 * @param context Application context
	 * @return Cache {@link File directory}.<br />
	 * <b>NOTE:</b> Can be null in some unpredictable cases (if SD card is unmounted and
	 * {@link android.content.Context#getCacheDir() Context.getCacheDir()} returns null).
	 */
	public static File getCacheDirectory(Context context) {
		return getCacheDirectory(context, true);
	}

	/**
	 * Returns application cache directory. Cache directory will be created on SD card
	 * <i>("/Android/data/[app_package_name]/cache")</i> (if card is mounted and app has appropriate permission) or
	 * on device's file system depending incoming parameters.
	 *
	 * @param context        Application context
	 * @param preferExternal Whether prefer external location for cache
	 * @return Cache {@link File directory}.<br />
	 * <b>NOTE:</b> Can be null in some unpredictable cases (if SD card is unmounted and
	 * {@link android.content.Context#getCacheDir() Context.getCacheDir()} returns null).
	 */
	public static File getCacheDirectory(Context context, boolean preferExternal) {
		File appCacheDir = null;
		String externalStorageState;
		try {
			externalStorageState = Environment.getExternalStorageState();
		} catch (NullPointerException e) { // (sh)it happens (Issue #660)
			externalStorageState = "";
		}
		if (preferExternal && MEDIA_MOUNTED.equals(externalStorageState) && hasExternalStoragePermission(context)) {
			appCacheDir = getExternalCacheDir(context);
		}
		if (appCacheDir == null) {
			appCacheDir = context.getCacheDir();
		}
		if (appCacheDir == null) {
			String cacheDirPath = "/data/data/" + context.getPackageName() + "/cache/";
			L.w("Can't define system cache directory! '%s' will be used.", cacheDirPath);
			appCacheDir = new File(cacheDirPath);
		}
		return appCacheDir;
	}

	/**
	 * Returns individual application cache directory (for only image caching from ImageLoader). Cache directory will be
	 * created on SD card <i>("/Android/data/[app_package_name]/cache/uil-images")</i> if card is mounted and app has
	 * appropriate permission. Else - Android defines cache directory on device's file system.
	 *
	 * @param context Application context
	 * @return Cache {@link File directory}
	 */
	public static File getIndividualCacheDirectory(Context context) {
		File cacheDir = getCacheDirectory(context);
		File individualCacheDir = new File(cacheDir, INDIVIDUAL_DIR_NAME);
		if (!individualCacheDir.exists()) {
			if (!individualCacheDir.mkdir()) {
				individualCacheDir = cacheDir;
			}
		}
		return individualCacheDir;
	}

	/**
	 * Returns specified application cache directory. Cache directory will be created on SD card by defined path if card
	 * is mounted and app has appropriate permission. Else - Android defines cache directory on device's file system.
	 *
	 * @param context  Application context
	 * @param cacheDir Cache directory path (e.g.: "AppCacheDir", "AppDir/cache/images")
	 * @return Cache {@link File directory}
	 */
	public static File getOwnCacheDirectory(Context context, String cacheDir) {
		File appCacheDir = null;
		if (MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) && hasExternalStoragePermission(context)) {
			appCacheDir = new File(Environment.getExternalStorageDirectory(), cacheDir);
		}
		if (appCacheDir == null || (!appCacheDir.exists() && !appCacheDir.mkdirs())) {
			appCacheDir = context.getCacheDir();
		}
		return appCacheDir;
	}

	private static File getExternalCacheDir(Context context) {
		File dataDir = new File(new File(Environment.getExternalStorageDirectory(), "Android"), "data");
		File appCacheDir = new File(new File(dataDir, context.getPackageName()), "cache");
		if (!appCacheDir.exists()) {
			if (!appCacheDir.mkdirs()) {
				L.w("Unable to create external cache directory");
				return null;
			}
			try {
				new File(appCacheDir, ".nomedia").createNewFile();
			} catch (IOException e) {
				L.i("Can't create \".nomedia\" file in application external cache directory");
			}
		}
		return appCacheDir;
	}

	private static boolean hasExternalStoragePermission(Context context) {
		int perm = context.checkCallingOrSelfPermission(EXTERNAL_STORAGE_PERMISSION);
		return perm == PackageManager.PERMISSION_GRANTED;
	}
}