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前言

Android开发过程可能需要用到的代码片段，一共35则。供需要时借鉴参考。

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);
 }

判断设备是否是平板

一般是7存以上是平板，此为官方用法。

public static boolean isTablet(Context context) {
 return (context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_LARGE;
 }

文字根据状态栏更改颜色

属性为:android:textColor此代码文件放置在项目的res/color/目录下:

<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>

背景色根据状态更改颜色

属性为:android:backgroup,如果直接给背景色将会报错:

<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>

启动App默认的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);
 }
 }

计算字宽

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);
 }

获取应用程序下所有的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;
}

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;
 }

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();
 }

检查又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;
 }

使用TransitionDrawable实现渐变效果

比使用AlphaAnimation效果要好，可以避免出现闪烁问题。

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);
 }

扫描指定文件

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）徐奥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));

Dip转px

用途：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());
 }

获取已经安装的APK路径

代码:

PackageManager pm = getPackageManager();
 for (ApplicationInfo app : pm.getInstalledApplications(0)) {
 Log.d("PackageList", "package: " + app.packageName + ", sourceDir: " + app.sourceDir);
 }

将会获得以下输出:

package: com.tmobile.thememanager, sourceDir: /system/app/ThemeManager.apk
 package: com.touchtype.swiftkey, sourceDir: /data/app/com.touchtype.swiftkey-1.apk

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);
 }

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()));
 }

保存回复ListView当前为位置

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);
 }
 }

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;
 }

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());
 }

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());
 }
 }
 });
 }

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);
 }

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));

ip地址转成8位16进制串

ip:192.168.68.128 16 =>hex :c0a84480

/** 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 "";
 }

WebView保留缩放功能但隐藏缩放控件

注意：setDisplayZoomControls是在API Level 11中新增。

mWebView.getSettings().setSupportZoom(true);
 mWebView.getSettings().setBuiltInZoomControls(true);
 if (DeviceUtils.hasHoneycomb())
 mWebView.getSettings().setDisplayZoomControls(false);

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";
 }
 }

###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

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;
 }

展开、收起状态栏

用途：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();
 }
 }

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;
 }

ListView使用ViewHolder极简写法

用起来非常简练，将ViewHolder隐于无形。

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);

设置Activity透明

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。

<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>

代码切换全屏

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.

//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);

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);

获取设备上已安装并且可启动的应用列表

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。

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

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