tips和坑

记录那些经常用却又打死记不住的代码(一)

Posted by alonealice on 2017-07-20

在开发过程中，总会遇到很多其实经常写，但又死活记不住(也许是本人比较笨)，每次都需要google的一些代码。这篇文章就是记录那些代码，以方便以后快速找到。

跳转到系统图库页面

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Intent albumIntent = new Intent(Intent.ACTION_PICK);
albumIntent.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "image/*");
activity.startActivityForResult(albumIntent, 0);

跳转到系统相机页面

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Intent cameraIntent = new Intent("android.media.action.IMAGE_CAPTURE");
cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(new File(fileName)));
activity.startActivityForResult(getImageByCamera, 0);

判断程序是否在后台

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ActivityManager activityManager = (ActivityManager) context.getApplicationContext()
                .getSystemService(Context.ACTIVITY_SERVICE);
        String packageName = context.getApplicationContext().getPackageName();
        /**
         * 获取Android设备中所有正在运行的App
         */
        List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager
                .getRunningAppProcesses();
        if (appProcesses == null)
            return false;
        for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
            if (appProcess.processName.equals(packageName)
                    && appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                return true;
            }
        }
        return false;

发送/取消闹钟

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Intent intent = new Intent(context, AlarmClockBroadcast.class);
      // FLAG_UPDATE_CURRENT：如果PendingIntent已经存在，保留它并且只替换它的extra数据。
      // FLAG_CANCEL_CURRENT：如果PendingIntent已经存在，那么当前的PendingIntent会取消掉，然后产生一个新的PendingIntent。
      PendingIntent pi = PendingIntent.getBroadcast(context,
              id, intent,
              PendingIntent.FLAG_UPDATE_CURRENT);
      AlarmManager alarmManager = (AlarmManager) context
              .getSystemService(Context.ALARM_SERVICE);

          // 设置闹钟,当前版本为19（4.4）或以上使用精准闹钟
          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
              alarmManager.setExact(AlarmManager.RTC_WAKEUP, nextTime, pi);
          } else {
              alarmManager.set(AlarmManager.RTC_WAKEUP, nextTime, pi);
          }

//取消闹钟
           am.cancel(pi);

屏幕宽度高度

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DisplayMetrics dm = context.getResources().getDisplayMetrics();
int width=dm.widthPixels;
int height=dm.heightPixels;

Android获取StatusBar高度

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int x = 0, statusBarHeight = 0;
Class<?> c = Class.forName("com.android.internal.R$dimen");
Object obj = c.newInstance();
Field field = c.getField("status_bar_height");
x = Integer.parseInt(field.get(obj).toString());
statusBarHeight = context.getResources().getDimensionPixelSize(x);

获取设备的imsi

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TelephonyManager mTelephonyMgr = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
String imsi = mTelephonyMgr.getSubscriberId();

获取设备的imei

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TelephonyManager mTelephonyMgr = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
String imei = mTelephonyMgr.getDeviceId();

获取应用版本和版本号

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String appVersion=context.getPackageManager().getPackageInfo(context.getPackageName(), 0).versionName;
int appVersionCode=context.getPackageManager().getPackageInfo(context.getPackageName(), 0).versionCode;

获取屏幕亮度

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ContentResolver resolver = activity.getContentResolver();
int nowBrightnessValue = android.provider.Settings.System.getInt(
					resolver, Settings.System.SCREEN_BRIGHTNESS);

dp转px

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DisplayMetrics dm = context.getResources().getDisplayMetrics();
float density=dm.density;
int px= (int) (dp * density + 0.5f);

px转dp

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DisplayMetrics dm = context.getResources().getDisplayMetrics();
float density=dm.density;
int dp= (int) (px / density + 0.5f);

sp转px

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final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
int px=(int) (spValue * fontScale + 0.5f);

px转sp

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final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
int sp=(int) (pxValue / fontScale + 0.5f);

获取缓存文件

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File f =context.getExternalCacheDir();

获取SD卡路径

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File f =context.getExternalCacheDir();

获取根目录文件

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File f = context.getExternalFilesDir("");
    if(null==f){
      f = context.getFilesDir();
    }

写文件

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File file = new File(fileName);  
FileOutputStream fos = new FileOutputStream(file);  
byte [] bytes = write.getBytes();
fos.write(bytes);
fos.close();

读文件

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FileInputStream fin = new FileInputStream(fileName);
int length = fin.available();   
byte [] buffer = new byte[length];   
fin.read(buffer);       
fin.close();

读取assets或资源文件

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//InputStream is = activity.getResources().openRawResource(id)
InputStream is = activity.getAssets().open(filePath);
InputStreamReader inputStreamReader;
inputStreamReader = new InputStreamReader(is, "utf-8");
BufferedReader reader = new BufferedReader(inputStreamReader);
StringBuffer sb = new StringBuffer("");
String line;
while ((line = reader.readLine()) != null) {
      sb.append(line);
      sb.append("\n");
      }
return sb.toString();

Bitmap保存文件

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FileOutputStream fos = new FileOutputStream(file, false);
bitmap.compress(Bitmap.CompressFormat.JPEG,100, fos);
fos.flush();
fos.close();

Bitmap.Option的设置

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BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;//是否只解析边界（true,则解析返回null，但是option有outHeight和outWidth）
        BitmapFactory.decodeFile(res, options);
        options.inPreferredConfig= Bitmap.Config.ARGB_8888;//图片解码时使用的颜色模式(默认8888)
        options.inSampleSize =2;//缩放倍数（整数）
        options.inJustDecodeBounds = false;
        options.inBitmap=bitmap;//是否重用该bitmap
        options.inPremultiplied=true;//如果设置了true(默认是true)，那么返回的图片RGB都会预乘透明通道A后的颜色,
                                        // 系统View或者Canvas绘制图片,不建议设置为fase,否则会抛出异常,
                                        // 这是因为系统会假定所有图像都预乘A通道的已简化绘制时间.
                                        // 设置inPremultiplied的同时,设置inScale会导致绘制的颜色不正确.
        options.inDither=true; // 设置是否抖动处理图片(android N 被废弃)
        options.inMutable=true; // 是否是mutable可变的(BitmapFactory.decodeResource是可变的，BitmapFactory.decodeFile是不可变的)
        options.inScaled=true;  //是否缩放
        options.inDensity=400;  //设置位图的像素密度，即每英寸有多少个像素
        options.inTargetDensity=400;    //设置绘制位图的屏幕密度,与inScale和inDesity一起使用,来对位图进行放缩.
        options.inScreenDensity=400;    //表示正在使用的实际屏幕的像素密度.

Bitmap旋转角度

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ExifInterface exif = null;
        int degree = 0;
        try {
            exif = new ExifInterface(imgPath);
        } catch (IOException e) {
            e.printStackTrace();
            exif = null;
        }
        if (exif != null) {
            int ori = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION,  ExifInterface.ORIENTATION_UNDEFINED);
            switch (ori) {
                case ExifInterface.ORIENTATION_ROTATE_90:
                    degree = 90;
                    break;
                case ExifInterface.ORIENTATION_ROTATE_180:
                    degree = 180;
                    break;
                case ExifInterface.ORIENTATION_ROTATE_270:
                    degree = 270;
                    break;
                default:
                    degree = 0;
                    break;
            }
        }

MD5加密

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char hexDigits[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
		try {
			byte[] btInput = s.getBytes();
			// get MessageDigest Object
			MessageDigest mdInst = MessageDigest.getInstance("MD5");
			mdInst.update(btInput);
			// get Ciphertext
			byte[] md = mdInst.digest();
			// Ciphertext to byte
			int j = md.length;
			char str[] = new char[j * 2];
			int k = 0;
			for (int i = 0; i < j; i++) {
				byte byte0 = md[i];
				str[k++] = hexDigits[byte0 >>> 4 & 0xf];
				str[k++] = hexDigits[byte0 & 0xf];
			}
			return new String(str);
		} catch (Exception e) {
			e.printStackTrace();
			return "0";
		}

监听锁屏开屏

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IntentFilter filter = new IntentFilter();
      filter.addAction(Intent.ACTION_SCREEN_ON);//屏幕打开
      filter.addAction(Intent.ACTION_SCREEN_OFF);//屏幕关闭
      filter.addAction(Intent.ACTION_USER_PRESENT);//解锁
      context.registerReceiver(receiver, filter);

直接判断屏幕是否关闭

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PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
boolean isScreenOn = pm.isInteractive();

设置StatusBar颜色

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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
           Window window = activity.getWindow();
           window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
           window.setStatusBarColor(ContextCompat.getColor(activity,colorId));
       }

设置StatusBar透明

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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            activity.getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
            ((ViewGroup)activity.getWindow().getDecorView().findViewById(android.R.id.content)).getChildAt(0).setPadding(0, DeviceUtil.getStatusBarHeight(activity), 0, 0);
        }

设置MIUI状态栏主题

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boolean result = false;
       if (window != null) {
           Class clazz = window.getClass();
           try {
               int darkModeFlag = 0;
               Class layoutParams = Class.forName("android.view.MiuiWindowManager$LayoutParams");
               Field field = layoutParams.getField("EXTRA_FLAG_STATUS_BAR_DARK_MODE");
               darkModeFlag = field.getInt(layoutParams);
               Method extraFlagField = clazz.getMethod("setExtraFlags", int.class, int.class);
               if(dark){
                   extraFlagField.invoke(window,darkModeFlag,darkModeFlag);//状态栏透明且黑色字体
               }else{
                   extraFlagField.invoke(window, 0, darkModeFlag);//清除黑色字体
               }
               result=true;
           }catch (Exception e){

           }
       }
       return result;

设置Flyme状态栏主题

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boolean result = false;
      if (window != null) {
          try {
              WindowManager.LayoutParams lp = window.getAttributes();
              Field darkFlag = WindowManager.LayoutParams.class
                      .getDeclaredField("MEIZU_FLAG_DARK_STATUS_BAR_ICON");
              Field meizuFlags = WindowManager.LayoutParams.class
                      .getDeclaredField("meizuFlags");
              darkFlag.setAccessible(true);
              meizuFlags.setAccessible(true);
              int bit = darkFlag.getInt(null);
              int value = meizuFlags.getInt(lp);
              if (dark) {
                  value |= bit;
              } else {
                  value &= ~bit;
              }
              meizuFlags.setInt(lp, value);
              window.setAttributes(lp);
              result = true;
          } catch (Exception e) {

          }
      }
      return result;

时间Long类型转固定格式

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SimpleDateFormat simpleDateFormat=new SimpleDateFormat(style, Locale.getDefault());
return simpleDateFormat.format(new Date(time));



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