JAVA-ANDROID 日积月累！

来源：互联网发布：yii2.0如何引入js 编辑：程序博客网时间：2024/05/11 04:24

    public static int inetAddressToInt(Inet4Address inetAddr)            throws IllegalArgumentException {        byte [] addr = inetAddr.getAddress();        return ((addr[3] & 0xff) << 24) | ((addr[2] & 0xff) << 16) |                ((addr[1] & 0xff) << 8) | (addr[0] & 0xff);    }

把inet形式的ip地址转换成一个int型的数字。一个byte 8个字节，刚好。

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Android的几大layout：

FrameLayout：

RelativeLayout：

LinearLayout：

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JAVA的数据流的操作。

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判断SD卡可以正常工作的状态：

我看很多文档里是这样判断的：

Environment.getExternalStorageState() != nul

!Environment.getExternalStorageState() .equals("Enviroment.MEDIA_REMOVED")

以上判断都是不完全的，因为还有很多其他的状态。

最好的方式是：

Environment.getExternalStorageState() .equals("Enviroment.MEDIA_MOUNTED")

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网络连接：

    private boolean isWirelessEnabled(Context context) {  ConnectivityManager manager = (ConnectivityManager) context.getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);      if (manager == null) {  return false; }    NetworkInfo networkinfo = manager.getActiveNetworkInfo();     if (networkinfo == null || !networkinfo.isAvailable()) {  return false;  }    return true;}

    private void openWirelessSetting(Context context) {Intent intent = new Intent(Settings.ACTION_WIRELESS_SETTINGS);((Activity) context).startActivity(intent);}

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GPS：

private boolean isGPSProviderEnabled(Context context) {    ContentResolver cr = context.getContentResolver();    String providersAllowed = Settings.Secure.getString(cr, Settings.Secure.LOCATION_PROVIDERS_ALLOWED);      Log.i("GPSService", "providersAllowed:" + providersAllowed);    return providersAllowed.contains("gps");        }

    private void openLocationSetting(Context context) {Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);((Activity) context).startActivity(intent);}

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AlertDialog使用：

new AlertDialog.Builder(mContext).setTitle("GPS cannot use").setMessage("GPS service is close,some CameraWater function is unused").setCancelable(false).setPositiveButton("Open GPS",new DialogInterface.OnClickListener() {public void onClick(DialogInterface dialog,int which) {openLocationSetting(mContext);}}).setNegativeButton("Keep Use",new DialogInterface.OnClickListener() {public void onClick(DialogInterface dialog,int which) {Toast.makeText(mContext,"NO open GPS lacation service!",Toast.LENGTH_SHORT).show();}}).setCancelable(false).show();

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Camera：

case TopBar.FLASH_AUTO:parameters.setFlashMode(Camera.Parameters.FLASH_MODE_AUTO);mCamera.setParameters(parameters);break;case TopBar.FLASH_ON:parameters.setFlashMode(Camera.Parameters.FLASH_MODE_ON);mCamera.setParameters(parameters);break;case TopBar.FLASH_OFF:parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);mCamera.setParameters(parameters);break;case TopBar.BACK_CAMERA:Change2BackCamera();break;case TopBar.FRONT_CAMERA:Change2FrontCamera();break;

private void Change2BackCamera(){if (mCamera != null) {mCamera.stopPreview();mCamera.release();mCamera = null;mWhichCamera = BACK;}mCamera = Camera.open(BACK);try {mCamera.setPreviewDisplay(mHolder);mCamera.setDisplayOrientation(90);parameters = mCamera.getParameters();parameters.setFlashMode(Camera.Parameters.FLASH_MODE_AUTO);parameters.setPictureSize(1600, 1200);parameters.setPreviewSize(640, 480);mCamera.setParameters(parameters);mCamera.startPreview();} catch (IOException e) {e.printStackTrace();}}

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背景：

setBackgroundResource(R.drawable.category_bg_normal);
setBackgroundColor(0xff000000);

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