Android实用代码

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 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。

一、获取应用程序下所有Activity

   public static ArrayList getActivities(Context ctx) {
      ArrayList result = new ArrayList();
      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;
  }

二、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;
    }

三、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();
    }

四、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 list = packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);        return list.size() > 0;    }

五、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。

六、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。

七、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！

一、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

转载自这里。

二、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

三、泛型ArrayList转数组

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

四、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。

五、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;
    }

六、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());
    }

七、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() {

            @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());
                }
            }
        });
    }

1、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。

2、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))

3、 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

4、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。

5、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";
        }
    }

6、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();

    } // end of func

7、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;
    }

1、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

2、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;
    }

3、ListView使用ViewHolder极简写法

   public static extends View> T getAdapterView(View convertView, int id) {
        SparseArray viewHolder = (SparseArray) convertView.getTag();
         if (viewHolder == null) {
            viewHolder = new SparseArray();
            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。

4、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

5、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

6、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。

7、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 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。

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