private void setImageBitmap(ImageView imageView, Bitmap bitmap) {        // Use TransitionDrawable to fade in.        final TransitionDrawable td = new TransitionDrawable(new Drawable[] { new ColorDrawable(android.R.color.transparent), new BitmapDrawable(mContext.getResources(), bitmap) });        //noinspection deprecation            imageView.setBackgroundDrawable(imageView.getDrawable());        imageView.setImageDrawable(td);        td.startTransition(200);    }

比使用AlphaAnimation效果要好，可避免出现闪烁问题。

sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, uri));

    用途：从本软件新增、修改、删除图片、文件某一个文件（音频、视频）需要更新系统媒体库时使用，不必扫描整个SD卡。

 public static int dipToPX(final Context ctx, float dip) {        return (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dip, ctx.getResources().getDisplayMetrics());    }

用途：难免在Activity代码中设置位置、大小等，本方法就很有用了！ 

PackageManager pm = getPackageManager();    for (ApplicationInfo app : pm.getInstalledApplications(0)) {         Log.d("PackageList", "package: " + app.packageName + ", sourceDir: " + app.sourceDir);    }
输出如下：
　　　　 package: com.tmobile.thememanager, sourceDir: /system/app/ThemeManager.apk
	package: com.touchtype.swiftkey, sourceDir: /data/app/com.touchtype.swiftkey-1.apk

public static void putStringProcess(Context ctx, String key, String value) {        SharedPreferences sharedPreferences = ctx.getSharedPreferences("preference_mu", Context.MODE_MULTI_PROCESS);        Editor editor = sharedPreferences.edit();        editor.putString(key, value);        editor.commit();    }    public static String getStringProcess(Context ctx, String key, String defValue) {        SharedPreferences sharedPreferences = ctx.getSharedPreferences("preference_mu", Context.MODE_MULTI_PROCESS);        return sharedPreferences.getString(key, defValue);    }

1  @SuppressWarnings("unchecked")2     public static <T> T[] toArray(Class<?> cls, ArrayList<T> items) {3         if (items == null || items.size() == 0) {4             return (T[]) Array.newInstance(cls, 0);5         }6         return items.toArray((T[]) Array.newInstance(cls, items.size()));7     }

private void saveCurrentPosition() {        if (mListView != null) {            int position = mListView.getFirstVisiblePosition();            View v = mListView.getChildAt(0);            int top = (v == null) ? 0 : v.getTop();            //保存position和top        }    }        private void restorePosition() {        if (mFolder != null && mListView != null) {            int position = 0;//取出保存的数据            int top = 0;//取出保存的数据            mListView.setSelectionFromTop(position, top);        }    }

可以保存在Preference中或者是数据库中，数据加载完后再设置。

public static Intent getHotspotSetting() {        Intent intent = new Intent();        intent.setAction(Intent.ACTION_MAIN);        ComponentName com = new ComponentName("com.android.settings", "com.android.settings.TetherSettings");        intent.setComponent(com);        return intent;    }

 public static String getIp(Context ctx) {        return Formatter.formatIpAddress((WifiManager) ctx.getSystemService(Context.WIFI_SERVICE).getConnectionInfo().getIpAddress());    }

public static void sortFiles(File[] files) {        Arrays.sort(files, new Comparator<File>() {            @Override            public int compare(File lhs, File rhs) {                //返回负数表示o1 小于o2，返回0 表示o1和o2相等，返回正数表示o1大于o2。                 boolean l1 = lhs.isDirectory();                boolean l2 = rhs.isDirectory();                if (l1 && !l2)                    return -1;                else if (!l1 && l2)                    return 1;                else {                    return lhs.getName().compareTo(rhs.getName());                }            }        });    }