每次做一個功能的時候，或多或少都會遇到，很常見的一個方法，就是突然忘記了怎麼了去寫，不得不又去網上滿世界的去找，既耽誤了時間，也耽誤了精力，今天就為大家集錦了一些我們開發中常用我們卻又不常記的方法，更多Android文章，請關注我的微信公衆賬号（左邊最上邊二維碼）。
1.根據手機的分辨率從 dip 的機關 轉成為 px(像素)
public static int dip2px(Context context, float dpValue) {
final float scale = context.getResources().getDisplayMetrics().density;
return (int) (dpValue * scale + 0.5f);
}
2.根據手機的分辨率從 px(像素) 的機關 轉成為 dp
public static int px2dip(Context context, float pxValue) {
final float scale = context.getResources().getDisplayMetrics().density;
return (int) (pxValue / scale + 0.5f);
}
3.隐藏鍵盤
public void hintInputMethodManager(){
InputMethodManager imm = (InputMethodManager)
getSystemService(ActivityLiveInteractive.this.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(mEditMessage.getWindowToken(), 0);
}
4.顯示鍵盤
public void showInputMethodManager(){
InputMethodManager inputManager ＝(InputMethodManager)mEditMessage.getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
inputManager.showSoftInput(mEditMessage, 0);
}
5.給TextView上下左右添加圖檔：
Drawable drawable = getResources().getDrawable(圖檔資源id);
drawable.setBounds(0, 0, drawable.getMinimumWidth(),
drawable.getMinimumHeight());
youview.setCompoundDrawables(drawable, null, null, null);
6.擷取手機螢幕寬度
public static int getScreenWidth(Context context) {
WindowManager manager = (WindowManager) context
.getSystemService(Context.WINDOW_SERVICE);
Display display = manager.getDefaultDisplay();
return display.getWidth();
}
7.擷取手機螢幕高度
public static int getScreenHeight(Context context) {
WindowManager manager = (WindowManager) context
.getSystemService(Context.WINDOW_SERVICE);
Display display = manager.getDefaultDisplay();
return display.getHeight();
}
8.擷取gbs狀态：
public static boolean getGPSState(Context context) {
final LocationManager lm = (LocationManager) context
.getSystemService(Context.LOCATION_SERVICE);
if (lm == null)
return false;
return lm.isProviderEnabled("gps");
}
9.擷取應用名稱：
public static String getAppName(Context context,String packageName){
String appName = null;
try {
ApplicationInfo applicationInfo = context.getPackageManager()
.getPackageInfo(packageName, 0).applicationInfo;
appName = (String) context.getPackageManager().getApplicationLabel(
applicationInfo);
} catch (NameNotFoundException e) {
e.printStackTrace();
}
return appName;
}
10.擷取版本名稱：
public static String getVersionName(Context context,String packageName) {
String versionName = null;
try {
// 擷取軟體版本名稱，對應AndroidManifest.xml下android:versionName
versionName = context.getPackageManager().getPackageInfo(
packageName, 0).versionName;
} catch (NameNotFoundException e) {
e.printStackTrace();
}
return versionName;
}
11.擷取版本号：
public static int getVersionCode(Context context,String packageName) {
int versionCode = 0;
try {
// 擷取軟體版本号，對應AndroidManifest.xml下android:versionCode
versionCode = context.getPackageManager().getPackageInfo(
packageName, 0).versionCode;
} catch (NameNotFoundException e) {
e.printStackTrace();
}
return versionCode;
}
12.BitMap 轉 inputStream
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
InputStream isBm = new ByteArrayInputStream(baos .toByteArray());
13.BitMap 轉 byte[]
Bitmap defaultIcon = BitmapFactory.decodeStream(in);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
defaultIcon.compress(Bitmap.CompressFormat.JPEG, 100, stream);
byte[] bitmapdata = stream.toByteArray();
14.Drawable 轉 byte[]
Drawable d; // the drawable (Captain Obvious, to the rescue!!!)
Bitmap bitmap = ((BitmapDrawable)d).getBitmap();
ByteArrayOutputStream stream = new ByteArrayOutputStream();
defaultIcon.compress(Bitmap.CompressFormat.JPEG, 100, bitmap);
byte[] bitmapdata = stream.toByteArray();
15.byte[] 轉 Bitmap
Bitmap bitmap =BitmapFactory.decodeByteArray(byte[], 0,byte[].length);
16.擷取存儲卡路徑
File sdcardDir=Environment.getExternalStorageDirectory();
17.StatFs 看檔案系統空間使用情況
StatFs statFs=new StatFs(sdcardDir.getPath());
18.擷取手機sdk版本：
int sdkInt=Build.VERSION.SDK_INT;
19.擷取手機品牌：
String brand=android.os.Build.BRAND;
20.擷取目前時間：
Date date = new Date();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
String dateString = formatter.format(date);
21.檢查是否連接配接網絡：
public static boolean isConnected(Context context) {
ConnectivityManager connectMgr = (ConnectivityManager) context.getSystemService(context.CONNECTIVITY_SERVICE);
NetworkInfo mobNetInfo = connectMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
NetworkInfo wifiNetInfo = connectMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
if (mobNetInfo != null && mobNetInfo.isConnected()) {
return true;
}
if (wifiNetInfo != null && wifiNetInfo.isConnected()) {
return true;
}
return false;
}
22.檢查是否是Wi-Fi連接配接：
public static boolean isWifiConnected(Context paramContext) {
NetworkInfo localNetworkInfo = ((ConnectivityManager) paramContext.getSystemService(Context.CONNECTIVITY_SERVICE)).getActiveNetworkInfo();
return (localNetworkInfo != null) && (localNetworkInfo.getType() == 1);
}
23.退出程式三種方式：
public static void ExitApp(Context ctx) {
ActivityManager am = (ActivityManager)
ctx.getSystemService(Context.ACTIVITY_SERVICE);
am.restartPackage(ctx.getPackageName());
Intent startMain = new Intent(Intent.ACTION_MAIN);
startMain.addCategory(Intent.CATEGORY_HOME);
startMain.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
ctx.startActivity(startMain);
android.os.Process.killProcess(android.os.Process.myPid());
System.exit(0);
android.os.Process.killProcess(android.os.Process.myPid());
}
24.md5加密：
public static String md5(String s) {
try {
// Create MD5 Hash
MessageDigest digest = Java.security.MessageDigest
.getInstance("MD5");
digest.update(s.getBytes("UTF-8"));
byte messageDigest[] = digest.digest();
// Create Hex String
StringBuffer hexString = new StringBuffer();
for (byte b : messageDigest) {
if ((b & 0xFF) < 0x10)
hexString.append("0");
hexString.append(Integer.toHexString(b & 0xFF));
}
return hexString.toString();
} catch (NoSuchAlgorithmException e) {
return"";
} catch (UnsupportedEncodingException e) {
return"";
}
}
25.郵箱檢驗：
public static boolean isEmail(String strEmail) {
String checkemail ="^([a-z0-9A-Z]+[-|\\.]?)+[a-z0-9A-Z]@([a-z0-9A-Z]+(-[a-z0-9A-Z]+)?\\.)+[a-zA-Z]{2,}$";
Pattern pattern = Pattern.compile(checkemail);
Matcher matcher = pattern.matcher(strEmail);
return matcher.matches();
}
26.判斷字元串是否為空
public static boolean isNull(String string)
{
if (null == string ||"".equals(string)) {
return false;
}
return true;
}
27.傳回時間
public static String friendly_time(String sdate) {
Date time = toDate(sdate);
if(time ==null) {
return"Unknown";
}
String ftime = "";
Calendar cal = Calendar.getInstance();
//判斷是否是同一天
String curDate = dateFormater2.get().format(cal.getTime());
String paramDate = dateFormater2.get().format(time);
if(curDate.equals(paramDate)){
int hour = (int)((cal.getTimeInMillis() - time.getTime())/3600000);
if(hour == 0)
ftime = Math.max((cal.getTimeInMillis() - time.getTime()) / 60000,1)+"分鐘前";
else
ftime = hour+"小時前";
return ftime;
}
long lt = time.getTime()/86400000;
long ct = cal.getTimeInMillis()/86400000;
int days = (int)(ct - lt);
if(days == 0){
int hour = (int)((cal.getTimeInMillis() - time.getTime())/3600000);
if(hour == 0)
ftime = Math.max((cal.getTimeInMillis() - time.getTime()) / 60000,1)+"分鐘前";
else
ftime = hour+"小時前";
}
else if(days == 1){
ftime = "昨天";
}
else if(days == 2){
ftime = "前天";
}
else if(days > 2 && days <= 10){
ftime = days+"天前";
}
else if(days > 10){
ftime = dateFormater2.get().format(time);
}
return ftime;
}
28.判斷是否是今天
public static boolean isToday(String sdate){
boolean b =false;
Date time = toDate(sdate);
Date today = new Date();
if(time !=null){
String nowDate = dateFormater2.get().format(today);
String timeDate = dateFormater2.get().format(time);
if(nowDate.equals(timeDate)){
b = true;
}
}
return b;
}
29.按兩次後退出應用
if(event.getAction() == KeyEvent.ACTION_DOWN && KeyEvent.KEYCODE_BACK == keyCode) {
long currentTime = System.currentTimeMillis();
if((currentTime-touchTime)>=waitTime) {
Toast.makeText(this, "再按一次退出", Toast.LENGTH_SHORT).show();
touchTime = currentTime;
return true;
}else {
AppManager.getAppManager().appExit();
finish();
return false;
}
}
return true;
30.代碼添加布局：
AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, 64);
TextView text = new TextView(activity);
text.setLayoutParams(lp);
text.setTextSize(20);
text.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
text.setPadding(36, 0, 0, 0);
text.setText(s);
![與專家面對面：Android開發入門問與答[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)