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Screen size density independent pixel resolution


Terms Screen size, density, density independent pixel, resolution as a picture - pictogram.

Test your knowledge
Q: How to find out the phone screen size?
A: (By length of display diagonale in inch -  Not to measure a diagonal of device!!!)

Q: What resolution has 720 x 1280 display?
A: (921600 pixels)

Q: What does it mean "240 dpi" screen density?
A: (Display have density 240 x 240  dots - "Tri-color LED etc." - per every physical (real) square inch. If you have icon 240x240 pixels, this will just occupy an area of one square inch on the display.)

Q: Phone have screen density 240 dpi. Image for 160 dpi screen density have size 128x 128 pixels. What will be the size of the image for 240 dpi screen density?
A: (Calculate the virtual pixels size.   128 * (240/160)  =  192.  You have to resize image to new size 192 x 192 physical pixels and put into folder drawable-hdpi (high) ~240dpi  for phone with screen density 240 dpi. ) or use density independend pixels 128dp x 128dp.



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Save Instance State if device is rotated | save-instance-state-if-device-is-rotated

Try this trick.
In AndroidManifest - activity tag write this code
App hold data of a views if will to rotation of device.

 android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" />

WebView change height Android Example | webview-change-height-android-example

The Android WebView changing the height according to text size.
If you need to change the height to a minimum try this source:

//public void loadDataWithBaseURL (String baseUrl, String data, String mimeType, String encoding, String historyUrl) 
WebView _webView; // findById(.....
String entryContent = "";
	"blabol",//  javascript i styly
	entryContent, null,
	"utf-8", null


Android Studio hide delete import module | android-studio-hide-delete-import-module

Hide module - open dialog: File > Project Structure Ctrl + Alt + Shift + S

Hide module: in opened Dialog select module which will hidden and click on minus (left upper corner)


If module is hidden, you can permanetly delete module from disk. But if you want using module in future,  copy module into other folder (not into AndroidProjects folder and his subbfolders) and delete module permanetly from project and disc. Right mouse click on module and select from menu Delete.

If you want import the backup copy to project, use: File>New>Import mudule

How to clear or hide an ImageView in Android | how-to-clear-or-hide-an-imageview-in-android

// solution 1
ImageView imageView = (ImageView)findViewById(R.id.myimage);
// or

// solution 2  hide ImageView

// solution 3 resize ImageView 0, 0
 hImageViewSemafor.setLayoutParams(new LinearLayout.LayoutParams(0,0));

Android Studio reduce memory usage of PC | android-studio-reduce-memory-usage

File->Settings->Plugins and disable some plugins:

  • Google Cloud Testing

  • Google Cloud Tools Core

  • Google Cloud Tools for Android Studio

  • CVS Integration

  • Git Integration

  • GitHub

  • hg4idea

  • Subversion Integration

Use Emulator AVD with small memmory usage. For example: Virtual tablet with hight resolution have big memmory usage. Virtual phone with 240x320 resolution have small memmory usage.

Use instaed of Emulator, real device connected by USB (smarphone Samsung Galaxy or other recommended by Google whit debugable mode).

If you notice that Android Studio works slowly, consider the possibility to reduce the number of folders under antivirus protection.
Each antivirus check in your project consumes resources. You can significantly improve the performance, if you exclude certain folders from the antivirus protection.

Editace: 2015-11-29 12:26:12
Počet článků v kategorii: 397

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