Say I have following TextView in layout:
<TextView
android:id="#+id/txtLoginError"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/sz_12dp"
android:gravity="center"
android:text="#string/foo" />
Is it possible that I change #dimen/sz_12dp to point to static field in my custom class, for example:
public static class MyDimensions {
public static int topMarginInPixels = 99; // which would be referenced in some fashion like android:layout_marginTop="#class/MyDimensions.topMarginInPixels"
}
I am basically looking for a way to "databind" layout element for some experimentation; instead of loading view and then modifying it in code (findview, setWeight, etc) I would like for view during creation to fetch sizes from my custom class like it fetches it from R.java.
NOTE: I know best practices for supporting multiple screens, differences between px & dp, how to provide different res/values directories for different screen sizes, so please response only if you know answer to this questions rather than repeat what can be read on this link.
It's not possible to achieve what you described, but if you really want to have pixels and only pixels you can very well put px size instead of dp, both in XML or in dimens file - but I guess you knew that already.
EDIT a dimension cannot be changed indeed at runtime, but it is not even supposed to; if you want to change a dimension at runtime for a view, get its LayoutParams object and set its width, height, margin, padding or whatever you want to change.
Related
When I design a layout, I centralize all dimensions in dimens.xml because of topics of maintainability. My question is if this is correct or not. What would it be the best good practice? There is very little information about this, nothing. I know it's good idea to centralize all strings of a layout on strings.xml, colors on colors.xml. But about dimensions?
For example:
<TableLayout
android:id="#+id/history_detail_rows_submitted"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/cebroker_history_detail_rows_border"
android:collapseColumns="*">
<TableRow
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/history_detail_rows_margin_vertical"
android:background="#color/cebroker_history_detail_rows_background"
android:gravity="center"
android:paddingBottom="#dimen/history_detail_rows_padding_vertical"
android:paddingLeft="#dimen/history_detail_rows_padding_horizontal"
android:paddingRight="#dimen/history_detail_rows_padding_horizontal"
android:paddingTop="#dimen/history_detail_rows_padding_vertical">
<TextView
android:layout_width="match_parent"
android:drawableLeft="#mipmap/ic_history_detail_submitted_by"
android:drawablePadding="#dimen/history_detail_rows_textviews_padding_drawable"
android:gravity="left|center"
android:paddingRight="#dimen/history_detail_rows_textviews_padding"
android:text="#string/history_detail_textview_submitted_by"
android:textColor="#color/cebroker_history_detail_rows_textviews"
android:textSize="#dimen/history_detail_rows_textviews_text_size" />
How to use dimens.xml
Create a new dimens.xml file by right clicking the values folder and choosing New > Values resource file. Write dimens for the name. (You could also call it dimen or dimensions. The name doesn't really matter, only the dimen resource type that it will include.)
Add a dimen name and value.
<?xml version="1.0" encoding="utf-8"?>
<resources>
<dimen name="my_value">16dp</dimen>
</resources>
Values can be in dp, px, or sp.
Use the value in xml
<TextView
android:padding="#dimen/my_value"
... />
or in code
float sizeInPixels = getResources().getDimension(R.dimen.my_value);
When to use dimens.xml
Thanks to this answer for more ideas.
Reusing values - If you need to use the same dimension multiple places throughout your app (for example, Activity layout padding or a TextView textSize), then using a single dimen value will make it much easier to adjust later. This is the same idea as using styles and themes.
Supporting Multiple Screens - A padding of 8dp might look fine on a phone but terrible on a 10" tablet. You can create multiple dimens.xml to be used with different screens. That way you could do something like set 8dp for the phone and 64dp for the tablet. To create another dimens.xml file, right click your res folder and choose New > Value resource file. (see this answer for details)
Convenient dp to px code conversion - In code you usually need to work with pixel values. However you still have to think about the device density and the conversion is annoying to do programmatically. If you have a constant dp value, you can get it in pixels easy like this for float:
float sizeInPixels = getResources().getDimension(R.dimen.my_value);
or this for int :
int sizeInPixels = getResources().getDimensionPixelSize(R.dimen.my_value);
I give many more details of how to do these things in my fuller answer.
When not to use dimens.xml
Don't put your values in dimens.xml if it is going to make them more difficult to maintain. Generally that will be whenever it doesn't fall into the categories I listed above. Using dimens.xml makes the code harder to read because you have to flip back and forth between two files to see what the actual values are. It's not worth it (in my opinion) for individual Views.
Strings are different. All strings should go in a resource file like strings.xml because almost all strings need to be translated when internationalizing your app. Most dimension values, on the other hand, do not need to change for a different locality. Android Studio seems to support this reasoning. Defining a string directly in the layout xml will give a warning but defining a dp value won't.
add an xml file dimens.xml this is use for support multiple devices.
<resources>
<!-- Default screen margins, per the Android Design guidelines. -->
<dimen name="iconarrow">1dp</dimen>
<item name="text_view_padding" type="integer">100</item>
</resources>
then you can use it in your code like this in java code
textview.setPadding(0, 0, 0, getResources().getInteger(R.integer.text_view_padding));
You can also use in other layout(xml file).
android:padding="#dimen/text_view_padding"
you don't need to mention dimen value in value folder file. this library auto manage all the things you just call like that
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/_20sdp"
android:paddingLeft="#dimen/_20sdp"
android:paddingRight="#dimen/_20sdp"
android:paddingTop="#dimen/_20sdp"
android:background="#color/colorPrimary"
android:orientation="vertical"
>
whole code click here for that
But about dimensions?
According to the official Android docs "A dimension is a simple resource that is referenced using the value provided in the name attribute (not the name of the XML file). As such, you can combine dimension resources with other simple resources in the one XML file, under one <resources> element"
For more details refer to http://developer.android.com/guide/topics/resources/more-resources.html
In this post, Devunwired gives three great reasons as to why use dimens.xml When should the dimens.xml file be used in Android?
#Jesús Castro You are doing it right. Maintaining values in the dimens.xml file is better than littering hardcoded values around in all your layout files.
For example, imagine the case where you to increase the left and right margins in all your view. If you used a single value maintained in dimens.xml, this would be a quick change - a single value in a single file.
However, if you had put the margin values as a literal values such as "16dp" in your layout files (instead of using a dimens value like "#dimen/leftright_margin"), you have to go edit each layout file which is error prone and just plain time consuming.
I have a novel method I use which I thought is in keeping with the question. I have been avoiding Xml alot to avoid the cost of parsing xml code.
Rather than using xml dimens ,I use java constants.
either...
public interface DimenConstants { ... }
or...
public class DimenConstants
{
public static void init(Activity activity){...}
}
Then in the case of supporting different screen, you can actually do this yourself in Java at runtime. One way is:
public class TestScreenSizes extends Activity
{
public static final ViewGroup.LayoutParams MAIN_VIEW_SPEC = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
#Override protected void onCreate(Bundle savedState)
{
super.onCreate(savedState);
setContentView(newTextView(),MAIN_VIEW_SPEC);
}
protected TextView newTextView()
{
TextView tv = new TextView(this);
DisplayMetrics display = getResources().getDisplayMetrics();
int resolution = display.widthPixels * display.heightPixels;
if(resolution == 1024) tv.setText("You are using an iphone");
else if(resolution == 4096) tv.setText("You are using a Samsung Galexy");
return rv;
}
}
yes absolutely It is best to keep the values in the dimens.xml file
I don’t know if it can help you but I wrote a little java programe that allows you to duplicate
a dimension xml file with a new desired value so that you no longer have to do it by hand line by line.
https://github.com/Drex-xdev/Dimensions-Scalable-Android
good day,
I was wondering, probably i do something wrong but i don't get it.
i defined
<dimen name="title">16sp</dimen>
When i set it in xml with something like
<TextView android:textSize="#dimen/title"/>
i get a different size (smaller) then when i set it in code.
int mTitleSize = res.getDimension(R.dimen.title);
textView.setTextSize(mTitleSize );
I also tried
tv.setTextSize(TypedValue.COMPLEX_UNIT_SP, mTitleSize);
But that results in the same text size (still biger then the textview in xml.
Does anyone has the same experience/encoutered the same probleem and have a solution (or just a solution)?
Thanks
I have extended the TextView and added support for borders, the thing is when I am drawing a border I need to put padding on the bordered side, so that the text would move.
I set my widths of borders in pixels, and it draws them accordingly, but on my TF201 tablet when I setPadding on the TextView, out of some reason it multiplies the padding width by 3x in pixels even though the setpadding documentation says it is defined explicitly in pixels.
EDIT:
Even though the answer I have selected is not what was causing my issue, it is a valid answer. The real answer to my question is actually a duplicate from this. Problem was that I have added a value to my padding each time setPadding was called. And it does get called three times on a page that has scrolling to it.
It might be a issue of pixel density. Its true that setpadding docs asks to set the padding in pixels but are you setting it in px, sp or dp ? If you read Supporting Different Densities document it says and I quote:
Different screens have different pixel densities,so the same number of pixels may correspond to different physical sizes on different devices.
So, when you specify spacing between two views, use dp rather than px:
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/clickme"
android:layout_marginTop="20dp" />
When specifying text size, always use sp:
<TextView android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="20sp" />
Also, based on your comments:
drawRect unit issues android andDraw Rectangle which change size w.r.t different android screen size question might help.
While the method may only accept pixel values, that sadly doesn't save you from needing to take screen densities into account. Instead, you need to determine your values in terms of DP and then programmatically calculate the pixel equivalents at runtime. Fortunately, there are some built-in methods to help you out. This can be done with the following code:
/// Converts 14 dip into its equivalent px
int dimensionInDp = 14;
Resources r = getResources();
float dimensionInPixels = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dimensionInDp, r.getDisplayMetrics());
Although the result is a float, you can easily cast it to an int for use in your setPadding(...) method.
(Referencing: Converting pixels to dp)
I have developed this custom ImageView class to override some of the default behavior to fit my needs. Let me describe what this custom ImageView does...
Let's say you have a bunch of icons to display in GridView both in the drawable-mdpi and drawable-hdpi folder, they are 48x48px and 72x72px in size, respectively. There are no icons available in the drawable-xhdpi folder. The GridView attributes are so that all the icons size will be in 48x48dp (this will translate to 48px, 72px and 96px for mpdi, hdpi and xhdpi densities, respectively).
Since there are no icons in the drawable-xhdpi folder, when this app is ran on a device with such density, the icons will be pulled from the drawable-hdpi folder. And since they are only 72px and the xhdpi devices are expecting 96px images, the icons will be stretched to fill the remaining pixels.
This is the behavior my custom ImageView attempts to override. With my custom component, what will happen is that the images will simply not get stretched. For instance, in the example above using my class, each ImageView inside the GridView will still be 96x96px (because of the 48x48dp size defined) but the images used are from the drawable-hdpi folder which are 72x72px. What will happen is that these images from the drawable-hdpi folder will be placed in the center of the ImageView which is 96x96px in size without stretching the image to fit the whole view size.
If the above is confusing, let's try with a few pictures. The example below does not use GridView, I'm trying to simplify the idea behind my custom class. These are the source pictures I'm using for this example:
This is the result on HDPI device:
And this is the result on XHDPI device:
The code for the layout on the screenshots above is this:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="10dp"
android:orientation="vertical">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Standard ImageView:"
android:textAppearance="?android:attr/textAppearanceLarge"/>
<ImageView
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_margin="10dp"
android:scaleType="center"
android:background="#FFEEEE"
android:src="#drawable/ic_female"/>
<ImageView
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_margin="10dp"
android:scaleType="center"
android:background="#FFEEEE"
android:src="#drawable/ic_male"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Custom UnscaledImageView:"
android:textAppearance="?android:attr/textAppearanceLarge"/>
<com.sampleapp.widget.UnscaledImageView
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_margin="10dp"
android:scaleType="center"
android:background="#FFEEEE"
android:src="#drawable/ic_female"/>
<com.sampleapp.widget.UnscaledImageView
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_margin="10dp"
android:scaleType="center"
android:background="#FFEEEE"
android:src="#drawable/ic_male"/>
</LinearLayout>
Is it more clear now? This is what I want to do and this is working nicely, besides a small performance issue... Now let me post the code I'm using for such custom component:
attrs.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="UnscaledImageView">
<attr name="android:src" />
</declare-styleable>
</resources>
UnscaledImageView.java:
public class UnscaledImageView extends ImageView {
private int mDeviceDensityDpi;
public UnscaledImageView(Context context) {
super(context);
mDeviceDensityDpi = getResources().getDisplayMetrics().densityDpi;
}
public UnscaledImageView(Context context, AttributeSet attrs) {
super(context, attrs);
mDeviceDensityDpi = getResources().getDisplayMetrics().densityDpi;
TypedArray styledAttrs = context.obtainStyledAttributes(attrs, R.styleable.UnscaledImageView);
int resourceId = styledAttrs.getResourceId(R.styleable.UnscaledImageView_android_src, 0);
if(resourceId != 0) {
setUnscaledImageResource(resourceId);
}
styledAttrs.recycle();
}
public void setUnscaledImageResource(int resId) {
setImageBitmap(decodeBitmapResource(resId));
}
#SuppressWarnings("deprecation")
public void setUnscaledBackgroundResource(int resId) {
BitmapDrawable drawable = new BitmapDrawable(null, decodeBitmapResource(resId));
drawable.setTargetDensity(mDeviceDensityDpi);
drawable.setGravity(Gravity.CENTER);
setBackgroundDrawable(drawable);
}
private Bitmap decodeBitmapResource(int resId) {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inDensity = mDeviceDensityDpi;
return BitmapFactory.decodeResource(getResources(), resId, options);
}
}
So, this class will do it's thing if the UnscaledImageView view is used in XML layouts or directly initialized in code. I've also provided 2 methods so the image can be changed in code while keeping it from being stretched. As you can see, these methods only take resource ids, so far I haven't felt the need to use drawables or bitmaps directly.
Now the real issue I'm having with this...
If this class is used as single image view in some layout, no problem, it's only decoding one image. But if it's used in a GridView where there can be like 40 icons (I'm taking this value from what really happens on my app running on my xhdpi device) visible at the same time, scrolling the GridView will be very slow because the decodeBitmapResource() is calling BitmapFactory.decodeResource() for each and every image.
This is my problem and that is my question. How can I optimize this? If possible, at all...
Putting those images into the res/drawable-nodpi/ could do what you want (I'm saying to put different resolution images side by side).
It would be a bit tricky because probably you'd have to follow a naming convention to be able to find the best resource for a given image that you are trying to draw. Probably this will require you to try finding images by their name and that's not a very efficient way to retrieve resources.
The way I imagin this is: on the layout (or anywhere else), you specify the name (string, not id!) of the image resource you want to use.
In that nodpi folder, you'd have the images with a suffix for the intended screen density.
Then, in the setter method you have to try different combinations in order to find the best available resource.
Problem for you to think: what if you're scaling down an image? The resource would be bigger than the view where you'd draw it!
Although the answer by Pedro Loureiro could be a possible solution, I decided to take a different approach after realizing something...
I've timed both the native ImageView loading and my UnscaledImageView loading in a GridView, non-scientifically of course and I've realized that my class loads all the images a little bit faster than the native one. Maybe the native methods have something else going on, besides decoding the resource (they still have to do it, right?) while my class simply decodes a resource (using BitmapFactory) and that's basically it.
I thought that it was my class that was making the GridView kinda slow while scrolling but after a few more tests, using the original ImageView without any tweaks, also revealed to be a little choppy while scrolling the GrivView.
The solution I found to solve this issue (either with my class or the native one) was to cache the icons in the GridView and for that I used the LruCache which is the recommended way of caching images in a GridView.
So that's the solution I'll be using to solve my issue. For more details please refer to the official training guide: http://developer.android.com/training/displaying-bitmaps/cache-bitmap.html
For reference, I've also found the following tutorial useful: http://andrewbrobinson.com/2012/03/05/image-caching-in-android/
I'm having a problem with my images and buttons in Android. Basically, when i define their graphics, I use the "setImageDrawable" method. But this method makes the image enlarge and 'overfill' the view like this:
http://img36.imageshack.us/img36/7713/screenshot20120330at211.png
While what I should get is:
http://img850.imageshack.us/img850/883/screenshot20120330at214.png
The second picture is what I get when I use "setBackgroundDrawable" instead of "setImageDrawable". But it's not the right way to do it so... here is my code so you can see how I proceed:
// Button "myButton" initialization
this.btn_connexion_off_480x800 = new ImageButton(this.getContext()); // ImageButton instantiation
this.btn_connexion_off_480x800.setBackgroundColor(Color.TRANSPARENT); // Paramétrage du background
this.btn_connexion_off_480x800.setImageDrawable(getResources().getDrawable(R.drawable.btn_connexion_off_480x800)); // Graphic source definition
this.btn_connexion_off_480x800.setPadding(0, 0, 0, 0); // Paramétrage des marges intérieures
this.img_header_480x800.addView(this.btn_connexion_off_480x800, new AbsoluteLayout.LayoutParams(114, 50, 8, 12)); // Binding to the super view and setting coordinates
Does anyone knows why is this happening ?
Yes, you are setting src to some fixed layout without setting its scale type, do following:
Use ImageView instead of ImageButton, and set an extra property of imageview:
this.btn_connexion_off_480x800.setScaleType(ScaleType.FIT_XY);
I tried Using XML
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/Image"
android:layout_width="fill_parent"
android:layout_height="225px"
android:scaleType="fitXY"/>
try android:scaleType="centerCrop"
Try defining a scaleType for your ImageButton with setScaleType.
I would not define my layout in code try to do as much layout as possible in xml files to cleanly separate behaviour from view.
Also don't use an Absolute Layout with absolute pixel values. If you define the layout in xml use dp units as explained in the support multiple screens guide. Your current layout will only work on one display size. If you are using pixel values in code you need to scale them to match the device density, this is also explained in the support multiple screens guide.
One other small improvement is the method you are using to set the drawable. An ImageButton also defines the method setImageRessource, this will allow you to directly call:
this.btn_connexion_off_480x800.setImageRessource(R.drawable.btn_connexion_off_480x800);