实用的Android代码片段集合（精）详解手机开发

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

 1 <selector xmlns:android="http://schemas.android.com/apk/res/android"> 
 2     <item android:state_selected="true"> 
 3 　　　　 <shape>             
 4 　　　　　　　<gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" /> 
 5         </shape> 
 6 　　 </item> 
 7     <item android:state_focused="true"> 
 8 　　　　 <shape> 
 9             <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" /> 
10         </shape> 
11 　　 </item> 
12     <item android:state_pressed="true"> 
13 　　　　 <shape> 
14             <gradient android:angle="0" android:centerColor="#00a59f" android:endColor="#00a59f" android:startColor="#00a59f" /> 
15         </shape> 
16 　　 </item> 
17     <item> 
18 　　　　<shape> 
19             <gradient android:angle="0" android:centerColor="#00ff00" android:endColor="00ff00" android:startColor="00ff00" /> 
20         </shape> 
21 　　</item> 
22 </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

　　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); 
    }

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

 1  　　/** ip转16进制 */ 
 2     public static String ipToHex(String ips) { 
 3         StringBuffer result = new StringBuffer(); 
 4         if (ips != null) { 
 5             StringTokenizer st = new StringTokenizer(ips, "."); 
 6             while (st.hasMoreTokens()) { 
 7                 String token = Integer.toHexString(Integer.parseInt(st.nextToken())); 
 8                 if (token.length() == 1) 
 9                     token = "0" + token; 
10                 result.append(token); 
11             } 
12         } 
13         return result.toString(); 
14     } 
15     /** 16进制转ip */ 
16     public static String texToIp(String ips) { 
17         try { 
18             StringBuffer result = new StringBuffer(); 
19             if (ips != null && ips.length() == 8) { 
20                 for (int i = 0; i < 8; i += 2) { 
21                     if (i != 0) 
22                         result.append('.'); 
23                     result.append(Integer.parseInt(ips.substring(i, i + 2), 16)); 
24                 } 
25             } 
26             return result.toString(); 
27         } catch (NumberFormatException ex) { 
28             Logger.e(ex); 
29         } 
30         return ""; 
31     }

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

 1 　　public static String getNetworkTypeName(Context context) { 
 2         if (context != null) { 
 3             ConnectivityManager connectMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); 
 4             if (connectMgr != null) { 
 5                 NetworkInfo info = connectMgr.getActiveNetworkInfo(); 
 6                 if (info != null) { 
 7                     switch (info.getType()) { 
 8                     case ConnectivityManager.TYPE_WIFI: 
 9                         return "WIFI"; 
10                     case ConnectivityManager.TYPE_MOBILE: 
11                         return getNetworkTypeName(info.getSubtype()); 
12                     } 
13                 } 
14             } 
15         } 
16         return getNetworkTypeName(TelephonyManager.NETWORK_TYPE_UNKNOWN); 
17     } 
18     public static String getNetworkTypeName(int type) { 
19         switch (type) { 
20         case TelephonyManager.NETWORK_TYPE_GPRS: 
21             return "GPRS"; 
22         case TelephonyManager.NETWORK_TYPE_EDGE: 
23             return "EDGE"; 
24         case TelephonyManager.NETWORK_TYPE_UMTS: 
25             return "UMTS"; 
26         case TelephonyManager.NETWORK_TYPE_HSDPA: 
27             return "HSDPA"; 
28         case TelephonyManager.NETWORK_TYPE_HSUPA: 
29             return "HSUPA"; 
30         case TelephonyManager.NETWORK_TYPE_HSPA: 
31             return "HSPA"; 
32         case TelephonyManager.NETWORK_TYPE_CDMA: 
33             return "CDMA"; 
34         case TelephonyManager.NETWORK_TYPE_EVDO_0: 
35             return "CDMA - EvDo rev. 0"; 
36         case TelephonyManager.NETWORK_TYPE_EVDO_A: 
37             return "CDMA - EvDo rev. A"; 
38         case TelephonyManager.NETWORK_TYPE_EVDO_B: 
39             return "CDMA - EvDo rev. B"; 
40         case TelephonyManager.NETWORK_TYPE_1xRTT: 
41             return "CDMA - 1xRTT"; 
42         case TelephonyManager.NETWORK_TYPE_LTE: 
43             return "LTE"; 
44         case TelephonyManager.NETWORK_TYPE_EHRPD: 
45             return "CDMA - eHRPD"; 
46         case TelephonyManager.NETWORK_TYPE_IDEN: 
47             return "iDEN"; 
48         case TelephonyManager.NETWORK_TYPE_HSPAP: 
49             return "HSPA+"; 
50         default: 
51             return "UNKNOWN"; 
52         } 
53     }

27、Android解压Zip包

 1     /** 
 2      * 解压一个压缩文档 到指定位置 
 3      *  
 4      * @param zipFileString 压缩包的名字 
 5      * @param outPathString 指定的路径 
 6      * [url=home.php?mod=space&uid=2643633]@throws[/url] Exception 
 7      */ 
 8     public static void UnZipFolder(String zipFileString, String outPathString) throws Exception { 
 9         java.util.zip.ZipInputStream inZip = new java.util.zip.ZipInputStream(new java.io.FileInputStream(zipFileString)); 
10         java.util.zip.ZipEntry zipEntry; 
11         String szName = ""; 
12         while ((zipEntry = inZip.getNextEntry()) != null) { 
13             szName = zipEntry.getName(); 
14             if (zipEntry.isDirectory()) { 
15                 // get the folder name of the widget 
16                 szName = szName.substring(0, szName.length() - 1); 
17                 java.io.File folder = new java.io.File(outPathString + java.io.File.separator + szName); 
18                 folder.mkdirs(); 
19             } else { 
20                 java.io.File file = new java.io.File(outPathString + java.io.File.separator + szName); 
21                 file.createNewFile(); 
22                 // get the output stream of the file 
23                 java.io.FileOutputStream out = new java.io.FileOutputStream(file); 
24                 int len; 
25                 byte[] buffer = new byte[1024]; 
26                 // read (len) bytes into buffer 
27                 while ((len = inZip.read(buffer)) != -1) { 
28                     // write (len) byte from buffer at the position 0 
29                     out.write(buffer, 0, len); 
30                     out.flush(); 
31                 } 
32                 out.close(); 
33             } 
34         }//end of while 
35         inZip.close(); 
36     }//end of func

28、从assets中读取文本和图片资源

 1 　　/** 从assets 文件夹中读取文本数据 */ 
 2     public static String getTextFromAssets(final Context context, String fileName) { 
 3         String result = ""; 
 4         try { 
 5             InputStream in = context.getResources().getAssets().open(fileName); 
 6             // 获取文件的字节数 
 7             int lenght = in.available(); 
 8             // 创建byte数组 
 9             byte[] buffer = new byte[lenght]; 
10             // 将文件中的数据读到byte数组中 
11             in.read(buffer); 
12             result = EncodingUtils.getString(buffer, "UTF-8"); 
13             in.close(); 
14         } catch (Exception e) { 
15             e.printStackTrace(); 
16         } 
17         return result; 
18     } 
19      
20     /** 从assets 文件夹中读取图片 */ 
21     public static Drawable loadImageFromAsserts(final Context ctx, String fileName) { 
22         try { 
23             InputStream is = ctx.getResources().getAssets().open(fileName); 
24             return Drawable.createFromStream(is, null); 
25         } catch (IOException e) { 
26             if (e != null) { 
27                 e.printStackTrace(); 
28             } 
29         } catch (OutOfMemoryError e) { 
30             if (e != null) { 
31                 e.printStackTrace(); 
32             } 
33         } catch (Exception e) { 
34             if (e != null) { 
35                 e.printStackTrace(); 
36             } 
37         } 
38         return null; 
39     }

29、展开、收起状态栏

 1  　　public static final void collapseStatusBar(Context ctx) { 
 2         Object sbservice = ctx.getSystemService("statusbar"); 
 3         try { 
 4             Class<?> statusBarManager = Class.forName("android.app.StatusBarManager"); 
 5             Method collapse; 
 6             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) { 
 7                 collapse = statusBarManager.getMethod("collapsePanels"); 
 8             } else { 
 9                 collapse = statusBarManager.getMethod("collapse"); 
10             } 
11             collapse.invoke(sbservice); 
12         } catch (Exception e) { 
13             e.printStackTrace(); 
14         } 
15     } 
16     public static final void expandStatusBar(Context ctx) { 
17         Object sbservice = ctx.getSystemService("statusbar"); 
18         try { 
19             Class<?> statusBarManager = Class.forName("android.app.StatusBarManager"); 
20             Method expand; 
21             if (Build.VERSION.SDK_INT >= 17) { 
22                 expand = statusBarManager.getMethod("expandNotificationsPanel"); 
23             } else { 
24                 expand = statusBarManager.getMethod("expand"); 
25             } 
26             expand.invoke(sbservice); 
27         } catch (Exception e) { 
28             e.printStackTrace(); 
29         } 
30     }

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。

原创文章，作者：奋斗，如若转载，请注明出处：https://blog.ytso.com/6018.html

实用的Android代码片段集合（精）详解手机开发

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