android开发实用代码片段

这里积累了一些不常见确又很实用的代码，详情内容来自农民伯伯。博客园：http://www.cnblogs.com  农民伯伯： http://over140.cnblogs.com

1、 精确获取屏幕尺寸（例如：3.5、4.0、5.0寸屏幕） 

 public static double getScreenPhysicalSize(Activity ctx) {
         DisplayMetrics dm = new DisplayMetrics();
         ctx.getWindowManager().getDefaultDisplay().getMetrics(dm);
         double diagonalPixels = Math.sqrt(Math.pow(dm.widthPixels, 2) + Math.pow(dm.heightPixels, 2));
         return diagonalPixels / (160 * dm.density);
     }

一般是7寸以上是平板

 

2、 判断是否是平板（官方用法）

   

 public static boolean isTablet(Context context) {
         return (context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_LARGE;
     }

 

3、 文字根据状态更改颜色 android:textColor 

 <selector xmlns:android="http://schemas.android.com/apk/res/android">
     <item android:color="#53c1bd" android:state_selected="true"/>
     <item android:color="#53c1bd" android:state_focused="true"/>
     <item android:color="#53c1bd" android:state_pressed="true"/>
     <item android:color="#777777"/>
 </selector>

   放在res/color/目录下

 

4、背景色根据状态更改颜色 android:backgroup

 <selector xmlns:android="http://schemas.android.com/apk/res/android">

     <item android:state_selected="true"><shape>

             <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" />
         </shape></item>
     <item android:state_focused="true"><shape>
             <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" />
         </shape></item>
     <item android:state_pressed="true"><shape>
             <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" />
         </shape></item>
     <item><shape>
             <gradient android:angle="0" android:centerColor="#00ff00" android:endColor="00ff00" android:startColor="00ff00" />
         </shape></item>

 </selector>

如果直接给背景色color会报错。

 

5、 启动APK的默认Activity

 public static void startApkActivity(final Context ctx, String packageName) {
     PackageManager pm = ctx.getPackageManager();
     PackageInfo pi;
     try {
         pi = pm.getPackageInfo(packageName, 0);
         Intent intent = new Intent(Intent.ACTION_MAIN, null);
         intent.addCategory(Intent.CATEGORY_LAUNCHER);
         intent.setPackage(pi.packageName);

         List<ResolveInfo> apps = pm.queryIntentActivities(intent, 0);

         ResolveInfo ri = apps.iterator().next();
         if (ri != null) {
             String className = ri.activityInfo.name;
             intent.setComponent(new ComponentName(packageName, className));
             ctx.startActivity(intent);
         }
     } catch (NameNotFoundException e) {
         Log.e("startActivity", e);
     }
 }

 

7、计算字宽

   

 public static float GetTextWidth(String text, float Size) {
         TextPaint FontPaint = new TextPaint();
         FontPaint.setTextSize(Size);
         return FontPaint.measureText(text);
     }

注意如果设置了textStyle，还需要进一步设置TextPaint。 

8、获取应用程序下所有Activity

 <span style="font-size:14px;line-height: 1.5;"></span><pre name="code" class="java">public static ArrayList<String> getActivities(Context ctx) {
       ArrayList<String> result = new ArrayList<String>();
       Intent intent = new Intent(Intent.ACTION_MAIN, null);
       intent.setPackage(ctx.getPackageName());
       for (ResolveInfo info : ctx.getPackageManager().queryIntentActivities(intent, 0)) {
           result.add(info.activityInfo.name);
       }
       return result;
   }

9、检测字符串中是否包含汉字

 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;
     }

 

10、检测字符串中只能包含：中文、数字、下划线(_)、横线(-)

  

 public static boolean checkNickname(String sequence) {
        final String format = "[^\\u4E00-\\u9FA5\\uF900-\\uFA2D\\w-_]";
        Pattern pattern = Pattern.compile(format);
        Matcher matcher = pattern.matcher(sequence);
        return !matcher.find();
    }

 

11、检查有没有应用程序来接受处理你发出的intent

 public static boolean isIntentAvailable(Context context, String action) {
     final PackageManager packageManager = context.getPackageManager();
     final Intent intent = new Intent(action);
     List<ResolveInfo> list = packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
     return list.size() > 0;
 }

12、使用TransitionDrawable实现渐变效果 

 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。

 

13、 扫描指定的文件 

 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。

 

14、dip转px

 

 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！

15、获取已经安装APK的路径

 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

16、 多进程Preferences数据共享

 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);
     }

相关文章：http://zengrong.net/post/1687.htm

17、泛型ArrayList转数组

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

 

18、 保存恢复ListView当前位置

 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。 

 

19、调用 便携式热点和数据共享 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;
     }

 

20、 格式化输出IP地址

  

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

21、 文件夹排序（先文件夹排序，后文件排序）

 

 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());
                 }
             }
         });
     }

22、发送不重复的通知（Notification）

 public static void sendNotification(Context context, String title,
             String message, Bundle extras) {
         Intent mIntent = new Intent(context, FragmentTabsActivity.class);
         mIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
         mIntent.putExtras(extras);

         int requestCode = (int) System.currentTimeMillis();

         PendingIntent mContentIntent = PendingIntent.getActivity(context,
                 requestCode, mIntent, 0);

         Notification mNotification = new NotificationCompat.Builder(context)
                 .setContentTitle(title).setSmallIcon(R.drawable.app_icon)
                 .setContentIntent(mContentIntent).setContentText(message)
                 .build();
         mNotification.flags |= Notification.FLAG_AUTO_CANCEL;
         mNotification.defaults = Notification.DEFAULT_ALL;

         NotificationManager mNotificationManager = (NotificationManager) context
                 .getSystemService(Context.NOTIFICATION_SERVICE);

         mNotificationManager.notify(requestCode, mNotification);
     }

代码说明：关键点在这个requestCode，这里使用的是当前系统时间，巧妙的保证了每次都是一个新的Notification产生。 

 

23、代码设置TextView的样式

使用过自定义Dialog可能马上会想到用如下代码：

 new TextView(this,null,R.style.text_style);

但你运行这代码你会发现毫无作用！正确用法：

 new TextView(new ContextThemeWrapper(this, R.style.text_style))

 

24、 ip地址转成8位十六进制串

 /** ip转16进制 */
 public static String ipToHex(String ips) {
     StringBuffer result = new StringBuffer();
     if (ips != null) {
         StringTokenizer st = new StringTokenizer(ips, ".");
         while (st.hasMoreTokens()) {
             String token = Integer.toHexString(Integer.parseInt(st.nextToken()));
             if (token.length() == 1)
                 token = "0" + token;
             result.append(token);
         }
     }
     return result.toString();
 }

 /** 16进制转ip */
 public static String texToIp(String ips) {
     try {
         StringBuffer result = new StringBuffer();
         if (ips != null && ips.length() == 8) {
             for (int i = 0; i < 8; i += 2) {
                 if (i != 0)
                     result.append('.');
                 result.append(Integer.parseInt(ips.substring(i, i + 2), 16));
             }
         }
         return result.toString();
     } catch (NumberFormatException ex) {
         Logger.e(ex);
     }
     return "";
 }

ip:192.168.68.128 16  =>hex :c0a84480

 

25、WebView保留缩放功能但隐藏缩放控件

       

 mWebView.getSettings().setSupportZoom(true);
         mWebView.getSettings().setBuiltInZoomControls(true);
         if (DeviceUtils.hasHoneycomb())
               mWebView.getSettings().setDisplayZoomControls(false);

注意：setDisplayZoomControls是在API Level 11中新增。

 

26、获取网络类型名称

 public static String getNetworkTypeName(Context context) {
        if (context != null) {
            ConnectivityManager connectMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            if (connectMgr != null) {
                NetworkInfo info = connectMgr.getActiveNetworkInfo();
                if (info != null) {
                    switch (info.getType()) {
                    case ConnectivityManager.TYPE_WIFI:
                        return "WIFI";
                    case ConnectivityManager.TYPE_MOBILE:
                        return getNetworkTypeName(info.getSubtype());
                    }
                }
            }
        }
        return getNetworkTypeName(TelephonyManager.NETWORK_TYPE_UNKNOWN);
    }

    public static String getNetworkTypeName(int type) {
        switch (type) {
        case TelephonyManager.NETWORK_TYPE_GPRS:
            return "GPRS";
        case TelephonyManager.NETWORK_TYPE_EDGE:
            return "EDGE";
        case TelephonyManager.NETWORK_TYPE_UMTS:
            return "UMTS";
        case TelephonyManager.NETWORK_TYPE_HSDPA:
            return "HSDPA";
        case TelephonyManager.NETWORK_TYPE_HSUPA:
            return "HSUPA";
        case TelephonyManager.NETWORK_TYPE_HSPA:
            return "HSPA";
        case TelephonyManager.NETWORK_TYPE_CDMA:
            return "CDMA";
        case TelephonyManager.NETWORK_TYPE_EVDO_0:
            return "CDMA - EvDo rev. 0";
        case TelephonyManager.NETWORK_TYPE_EVDO_A:
            return "CDMA - EvDo rev. A";
        case TelephonyManager.NETWORK_TYPE_EVDO_B:
            return "CDMA - EvDo rev. B";
        case TelephonyManager.NETWORK_TYPE_1xRTT:
            return "CDMA - 1xRTT";
        case TelephonyManager.NETWORK_TYPE_LTE:
            return "LTE";
        case TelephonyManager.NETWORK_TYPE_EHRPD:
            return "CDMA - eHRPD";
        case TelephonyManager.NETWORK_TYPE_IDEN:
            return "iDEN";
        case TelephonyManager.NETWORK_TYPE_HSPAP:
            return "HSPA+";
        default:
            return "UNKNOWN";
        }
    }

 

27、Android解压Zip包

 /**
      * 解压一个压缩文档 到指定位置
      *
      * @param zipFileString 压缩包的名字
      * @param outPathString 指定的路径
      * @throws Exception
      */
     public static void UnZipFolder(String zipFileString, String outPathString) throws Exception {
         java.util.zip.ZipInputStream inZip = new java.util.zip.ZipInputStream(new java.io.FileInputStream(zipFileString));
         java.util.zip.ZipEntry zipEntry;
         String szName = "";

         while ((zipEntry = inZip.getNextEntry()) != null) {
             szName = zipEntry.getName();

             if (zipEntry.isDirectory()) {

                 // get the folder name of the widget
                 szName = szName.substring(0, szName.length() - 1);
                 java.io.File folder = new java.io.File(outPathString + java.io.File.separator + szName);
                 folder.mkdirs();

             } else {

                 java.io.File file = new java.io.File(outPathString + java.io.File.separator + szName);
                 file.createNewFile();
                 // get the output stream of the file
                 java.io.FileOutputStream out = new java.io.FileOutputStream(file);
                 int len;
                 byte[] buffer = new byte[1024];
                 // read (len) bytes into buffer
                 while ((len = inZip.read(buffer)) != -1) {
                     // write (len) byte from buffer at the position 0
                     out.write(buffer, 0, len);
                     out.flush();
                 }
                 out.close();
             }
         }//end of while

         inZip.close();

     }

28、 从assets中读取文本和图片资源

 /** 从assets 文件夹中读取文本数据 */
     public static String getTextFromAssets(final Context context, String fileName) {
         String result = "";
         try {
             InputStream in = context.getResources().getAssets().open(fileName);
             // 获取文件的字节数
             int lenght = in.available();
             // 创建byte数组
             byte[] buffer = new byte[lenght];
             // 将文件中的数据读到byte数组中
             in.read(buffer);
             result = EncodingUtils.getString(buffer, "UTF-8");
             in.close();
         } catch (Exception e) {
             e.printStackTrace();
         }
         return result;
     }

     /** 从assets 文件夹中读取图片 */
     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) {
             if (e != null) {
                 e.printStackTrace();
             }
         } catch (Exception e) {
             if (e != null) {
                 e.printStackTrace();
             }
         }
         return null;
     }