实用的Android代码片段集合（精）

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, ) + Math.pow(dm.heightPixels, ));
        return diagonalPixels / ( * 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, );
            Intent intent = new Intent(Intent.ACTION_MAIN, null);
            intent.addCategory(Intent.CATEGORY_LAUNCHER);
            intent.setPackage(pi.packageName);
            List<ResolveInfo> apps = pm.queryIntentActivities(intent, );
            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

　　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, )) {
          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() > ;
    }

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);
    }

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
      * [url=home.php?mod=space&uid=2643633]@throws[/url] 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();
     }//end of func

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;
     }

29、展开、收起状态栏

  　　public static final void collapseStatusBar(Context ctx) {
         Object sbservice = ctx.getSystemService("statusbar");
         try {
             Class<?> statusBarManager = Class.forName("android.app.StatusBarManager");
             Method collapse;
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
                 collapse = statusBarManager.getMethod("collapsePanels");
             } else {
                 collapse = statusBarManager.getMethod("collapse");
             }
             collapse.invoke(sbservice);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
     public static final void expandStatusBar(Context ctx) {
         Object sbservice = ctx.getSystemService("statusbar");
         try {
             Class<?> statusBarManager = Class.forName("android.app.StatusBarManager");
             Method expand;
             if (Build.VERSION.SDK_INT >= 17) {
                 expand = statusBarManager.getMethod("expandNotificationsPanel");
             } else {
                 expand = statusBarManager.getMethod("expand");
             }
             expand.invoke(sbservice);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

用途：可用于点击Notifacation之后收起状态栏

30、获取状态栏高度

    public static int getStatusBarHeight(Context context){
        Class<?> c = null;
        Object obj = null;
        Field field = null;
        int x = 0, statusBarHeight = 0;
        try {
            c = Class.forName("com.android.internal.R$dimen");
            obj = c.newInstance();
            field = c.getField("status_bar_height");
            x = Integer.parseInt(field.get(obj).toString());
            statusBarHeight = context.getResources().getDimensionPixelSize(x);
        } catch (Exception e1) {
            e1.printStackTrace();
        }
        return statusBarHeight;
    }

31、ListView使用ViewHolder极简写法

    public static <T extends View> T getAdapterView(View convertView, int id) {
        SparseArray<View> viewHolder = (SparseArray<View>) convertView.getTag();
        if (viewHolder == null) {
            viewHolder = new SparseArray<View>();
            convertView.setTag(viewHolder);
        }
        View childView = viewHolder.get(id);
        if (childView == null) {
            childView = convertView.findViewById(id);
            viewHolder.put(id, childView);
        }
        return (T) childView;
    }

用法：

　　　　@Override
   　　 public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_feed_item, parent, false);
        }
        ImageView thumnailView = getAdapterView(convertView, R.id.video_thumbnail);
        ImageView avatarView =  getAdapterView(convertView, R.id.user_avatar);
        ImageView appIconView = getAdapterView(convertView, R.id.app_icon);

用起来非常简练，将ViewHolder隐于无形。

32、设置Activity透明

　　<style name="TransparentActivity" parent="AppBaseTheme">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:colorBackgroundCacheHint">@null</item>
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowContentOverlay">@null</item>
    </style>

说明：AppBaseTheme一般是你application指定的android:theme是啥这里就是啥，否则Activity内部的空间风格可能不一致。

用途：用于模拟Dialog效果，比如再Service中没法用Dialog，就可以用Activity来模拟

33、代码切换全屏

　　　　 //切换到全屏
        getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN);
        getActivity().getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
        //切换到非全屏
        getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN);

注意：切换到全屏时，底部的虚拟按键仍然是显示的。次方法可多次调用用于切换

用途：播放器界面经常会用到

34、调用开发者选项中显示触摸位置功能

　　　　  android.provider.Settings.System.putInt(getContentResolver(), "show_touches", 1);

设置1显示，设置0不显示。

35、获取设备上已安装并且可启动的应用列表

　　　　　Intent intent = new Intent(Intent.ACTION_MAIN);

　　　　　intent.addCategory(Intent.CATEGORY_LAUNCHER);

　　　　　List<ResolveInfo> activities = getPackageManager().queryIntentActivities(intent, 0);

注意：使用getInstalledApplications会返回很多无法启动甚至没有图标的系统应用。

　　　　　　　　ResolveInfo.activityInfo.applicationInfo也能取到你想要的数据。