Android obtains the screen size and density

// Obtain the screen density (method 1) int screenWidth = getWindowManager (). getdefadisplay display (). getWidth (); // screen width (pixels, for example, 480px) int screenHeight = getWindowManager (). getdefadisplay display (). getHeight (); // screen height (pixel, for example, 800 p) Log. e (TAG + "getDefaultDisplay", "screenWidth =" + screenWidth + "; screenHeight =" + screenHeight); // obtain the screen density (method 2) displayMetrics dm = new DisplayMetrics (); dm = getResources (). getDisplayMetrics (); float density = dm. density; // screen density (pixel ratio: 0.75/1.0/1.5/2.0) int densityDPI = dm. densityDpi; // screen density (pixels per inch: 120/160/240/320) float xdpi = dm. xdpi; float ydpi = dm. ydpi; Log. e (TAG + "DisplayMetrics", "xdpi =" + xdpi + "; ydpi =" + ydpi); Log. e (TAG + "DisplayMetrics", "density =" + density + "; densityDPI =" + densityDPI); screenWidth = dm. widthPixels; // screen width (pixels, for example, 480px) screenHeight = dm. heightPixels; // The screen height (pixels, for example, 800px) Log. e (TAG + "DisplayMetrics (111)", "screenWidth =" + screenWidth + "; screenHeight =" + screenHeight); // obtain the screen density (method 3) dm = new DisplayMetrics (); getWindowManager (). getdefadisplay display (). getMetrics (dm); density = dm. density; // screen density (pixel ratio: 0.75/1.0/1.5/2.0) densityDPI = dm. densityDpi; // screen density (pixels per inch: 120/160/240/320) xdpi = dm. xdpi; ydpi = dm. ydpi; Log. e (TAG + "DisplayMetrics", "xdpi =" + xdpi + "; ydpi =" + ydpi); Log. e (TAG + "DisplayMetrics", "density =" + density + "; densityDPI =" + densityDPI); int screenWidthDip = dm. widthPixels; // screen width (dip, for example, 320dip) int screenHeightDip = dm. heightPixels; // screen width (dip, for example, 533dip) Log. e (TAG + "DisplayMetrics (222)", "screenWidthDip =" + screenWidthDip + "; screenHeightDip =" + screenHeightDip); screenWidth = (int) (dm. widthPixels * density + 0.5f); // screen width (px, for example: 480px) screenHeight = (int) (dm. heightPixels * density + 0.5f); // The screen height (px, for example, 800px) Log. e (TAG + "DisplayMetrics (222)", "screenWidth =" + screenWidth + "; screenHeight =" + screenHeight );

The test results are as follows:

E/== MyScreenActivity ===================================  getDefaultDisplay( 8509): screenWidth=320; screenHeight=533E/== MyScreenActivity ===================================  DisplayMetrics( 8509): xdpi=156.3077; ydpi=157.51938E/== MyScreenActivity ===================================  DisplayMetrics( 8509): density=1.0; densityDPI=160E/== MyScreenActivity ===================================  DisplayMetrics(111)( 8509): screenWidth=320; screenHeight=533E/== MyScreenActivity ===================================  DisplayMetrics( 8509): xdpi=234.46153; ydpi=236.27907E/== MyScreenActivity ===================================  DisplayMetrics( 8509): density=1.5; densityDPI=240E/== MyScreenActivity ===================================  DisplayMetrics(222)( 8509): screenWidthDip=320; screenHeightDip=533E/== MyScreenActivity ===================================  DisplayMetrics(222)( 8509): screenWidth=480; screenHeight=800

Analysis result:

 

In the onDraw () method

Methods 1 and 2 are the same, and the results are both 320*533, which is obviously not the size of the i9000 screen of the test machine.

Method 3: multiply the results obtained from methods 1 and 2 by the density, and then the perfect 480*800, perfect!

Note:If the density is greater than 1, you must set the targetSdkVersion to 4-9. For example:
<Uses-sdk android: minSdkVersion = "3" android: targetSdkVersion = "10"/>

 

 

However, does this mean that method 3 must be generic?

The answer is no, because I also tested it on the simulator, HTC G14 physical machine, ViewSonic, and Galaxy tablet. Method 3 amplified the actual screen value when density = 1.5, example: HTC G14

On HTC G14, the actual screen size is obtained through dm. widthPixels and dm. heightPixels (540,960)

The reason why the actual physical screen size cannot be obtained through a common method may be that the Android system is open-source and different mobile phone manufacturers do not have a uniform manufacturing standard to define the mobile phone screen.

 

Analyze the code carefully and find that the problem lies in the Code:

GetWindowManager (). getDefaultDisplay (). getMetrics (dm)

Initialize a DisplayMetrics object from this display's data.

 

Dm = getResources (). getDisplayMetrics ()

Return the current display metrics that are in effect for this resource object. The returned object shoshould be treated as read-only.