Android实用小代码

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);
}

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);
     }
}

6、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。

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();
}

11、使用TransitionDrawable实现图片显示的时候有渐变效果

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。

12、 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。

13、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！

14、获取已经安装APK（列表）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

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、 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

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、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))

23、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";
     }
}

24、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

25、 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;
}

26、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

27、 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;
}

28、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);

}

29、 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

30、 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

30、 控件绑定

 protected <T extends View> T findView(int id) {
        return (T) findViewById(id);}

这里面的方法有在项目中用到的，有平时整理的，以后会陆陆续续的在这里添加的。。。