Android screen self-adaptation

 

This is a serious problem that I recently encountered and cannot be solved perfectly. In desperation, I posted a question to the csdn Android version. I did not expect to disturb the moderator and gave me a lot of help, so that I can solve similar problems perfectly. I decided to wait for the csdn Android forum. Haha.

 

Problem description:

On the WVGA 854 device, the adaptive change of image size leads to incorrect results. In my project, the image will always be reduced.

For example, when an 8-54x90 image is adaptive, the image width and height will be reduced by 1.5 times, which will prevent full screen display.

 

Problem Analysis:

I found that the image read is normal, which is 854x90, and the density 240 is the same as the real machine. However, after a code sentence, the density becomes 160, the height, and the width is reduced by 1.5 times. This code is bitmapdrawable drawable = new bitmapdrawable (Bitmap );

 

Soon I found that this is because the density has changed. Android will automatically adapt the image according to the density, from 240 to 160, which is exactly 1.5 times the width, the height is also reduced by 1.5 times.

 

So I'm sure the problem is density, and it turns out that my judgment is correct.

 

Solution:

After reading the android development documentation, I found that the feature was added from Android 1.6 to adapt to changes based on density. The API of our project uses Android 1.5.

1.5 does not provide the corresponding API to adapt to the real machine's density, but uses a default density 160. this explains why density changes to 160 every time I pass bitmapdrawable.

 

In the 1.6 Documentation, the APIs used in our project have been deprected, and the density-based APIs are provided.

 

This is the constructor used in our project.

Bitmapdrawable (Bitmap Bitmap) This constructor is deprecated. UseBitmapDrawable(Resources, Bitmap) To ensure That the drawable has correctly set its target density.

 

After reading the API Doc, I used the following constructor:

 

Bitmapdrawable (Resources Res, bitmap Bitmap) Create drawable from a bitmap, setting initial target density based on The display metrics of the resources.

 

This API description clearly states that the initial target density will be set based on the real machine's density.

In this way, bitmapdrawable automatically changes the image based on the correct density.

 

The first parameter in the constructor is easily obtained. You can call activity. getresources () directly to obtain the parameter. The second parameter is our original map.

 

In this case, the problem is successfully solved.

 

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