Android 实用代码片段
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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 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>
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 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>
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;
}
//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);
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)
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