常用的代码片段，不断更新

/** 
* 给界面添加透明度 
*
 * @param activity
 * @param bgAlpha 
*/
public static void backgroundAlpha(Activity activity, float bgAlpha) { 
      activity.getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
      WindowManager.LayoutParams lp = activity.getWindow().getAttributes();   
      lp.alpha = bgAlpha; //0.0-1.0    
      activity.getWindow().setAttributes(lp);
}

public static int getVersionCode(Context context) {   
      int code = 0;    
      if (context == null) {        
      return code;   
      } try {        
      PackageInfo info =context.getPackageManager().getPackageInfo(context.getPackageName(), 0);          code = info.versionCode;   
            } catch (PackageManager.NameNotFoundException e) {
                    }   
      return code;
}

public static boolean isNetworkConnected(Context context) {    
if (context != null) {       
       ConnectivityManager mConnectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);        
       NetworkInfo mNetworkInfo = mConnectivityManager                .getActiveNetworkInfo();        
       if (mNetworkInfo != null) {            
             return mNetworkInfo.isAvailable() 
                         && mNetworkInfo.isConnectedOrConnecting();    
                                 } 
                     }    
       return false;
}

public static boolean isMobileConnected(Context context) {    
        if (context != null) {        
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);       
        NetworkInfo mMobileNetworkInfo = mConnectivityManager                .getNetworkInfo(ConnectivityManager.TYPE_MOBILE);        
        if (mMobileNetworkInfo != null) {            
               return  mMobileNetworkInfo.isAvailable() 
                       && mMobileNetworkInfo.isConnectedOrConnecting();        
                                        }    
                              }    
        return false;
}

public static boolean isWifi(Context context) {    
        if (context != null) {       
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context .getSystemService(Context.CONNECTIVITY_SERVICE);        
        NetworkInfo mNetworkInfo = mConnectivityManager                .getActiveNetworkInfo();       
        if (mNetworkInfo != null) {            
                return mNetworkInfo.getType() == ConnectivityManager.TYPE_WIFI;       
                                 }    
                              }   
        return false;
}

public static void setListViewHeightBasedOnChildren(ListView listView) {    
// 获取ListView对应的Adapter   
ListAdapter listAdapter = listView.getAdapter();    
if (listAdapter == null) { 
       return;   
}    
int totalHeight = 0;    
for (int i = 0; i < listAdapter.getCount(); i++) {        
View listItem = listAdapter.getView(i, null, listView);        
listItem.measure(0, 0); // 计算子项View 的宽高       
 totalHeight += listItem.getMeasuredHeight(); // 统计所有子项的总高度   
}    
ViewGroup.LayoutParams params = listView.getLayoutParams();    
params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));     
listView.setLayoutParams(params);
}

/** 
* 给界面添加透明度 
*  @param phoneNum 
*/
public void call(String phoneNum){
    Intent intent = new Intent(Intent.ACTION_CALL, Uri.parse("tel:"+ phoneNum));
    startActivity(intent);
}

public static boolean checkChinese(String sequence) {   
 final String format = "[\\u4E00-\\u9FA5\\uF900-\\uFA2D]";    
boolean result = false;    
Pattern pattern = Pattern.compile(format);    
Matcher matcher = pattern.matcher(sequence);    
result = matcher.find();   
 return result;
}

public static Drawable loadImageFromAsserts(final Context ctx, String fileName) {    try {        
   InputStream is = ctx.getResources().getAssets().open(fileName);       
   return Drawable.createFromStream(is, null);    
} catch (IOException e) {       
   if (e != null) {            
   e.printStackTrace();      
   }    
} catch (OutOfMemoryError e) {        i
   if (e != null) {            
   e.printStackTrace();       
 }    
} catch (Exception e) {      
  if (e != null) {           
  e.printStackTrace();   
  }  
  }   
 return null;
}

public static boolean isNull(String string) {    
  if (string != null) {        
  string = string.trim();        
  if (string.length() != 0) {            
  return false;        
  }    
  }    
  return true;
}