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[操作系统]Android 实用代码片段

一些不常见确又很实用的代码块。

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);  }

 

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 ="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>

4.背景色根据状态更改颜色 android:backgroup(如果直接给背景色color会报错)

<selector ="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>

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);    }  }

6.计算字宽(注意如果设置了textStyle,还需要进一步设置TextPaint)

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

7.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; }

8.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;  }

9.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();  } 

10.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;  }

11.使用TransitionDrawable实现渐变效果(比使用AlphaAnimation效果要好,可避免出现闪烁问题)

 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);  }

12.扫描指定的文件(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)

sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, uri));

13.Dip转px(难免在Activity代码中设置位置、大小等,本方法就很有用了)

public static int dipToPX(final Context ctx, float dip) {    return (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dip, ctx.getResources().getDisplayMetrics());  }

14.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);  }

15.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);  }

16.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()));  }

17.保存恢复ListView当前位置(可以保存在Preference中或者是数据库中,数据加载完后再设置)

 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);    }  }

18.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;  }

 

19.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());  }

20.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());        }      }    });  }

21.发送不重复的通知Notification(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)

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);  }

22.代码设置TextView的样式

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

23.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 "";  }

24.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);

25.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";    }  }

26.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

27.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;  }

28.展开、收起状态栏(可用于点击Notifacation之后收起状态栏)

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();    }  }

29.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;  }

30.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;  [email protected]  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);

31.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

32.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

33.调用开发者选项中显示触摸位置功能(设置1显示,设置0不显示)

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

 

34.获取设备上已安装并且可启动的应用列表(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)

Intent intent = new Intent(Intent.ACTION_MAIN);intent.addCategory(Intent.CATEGORY_LAUNCHER);List<ResolveInfo> activities = getPackageManager().queryIntentActivities(intent, 0)

 

转载自 农民伯伯: http://over140.cnblogs.com