Android drawable resource learning (6) and levellistdrawable

A levelistdrawable manages a set of alternate drawable resources. Each drawable resource in levelistdrawable is combined with a maximum value, which is an item of levellistdrawable resources.

You can call the setlevel () method of drawable to load a level-list or a drawable resource defined in the Code and determine how to load an item: Android of an item in level-list: if the maxlevel value is greater than or equal to the value set by setlevel, it is loaded.

File Location:

res/drawable/filename.xml
File name as resource ID

Compilation Resource Type:

Point to levellistdrawablePointer

Resource reference:

In Java: R.drawable.filename
In XML: @[package:]drawable/filename

Syntax:

<?xml version="1.0" encoding="utf-8"?><level-list    xmlns:android="http://schemas.android.com/apk/res/android" >    <item        android:drawable="@drawable/drawable_resource"        android:maxLevel="integer"        android:minLevel="integer" /></level-list>

Element:

<level-list>

Must be used as the root node. Contains multiple <item> nodes.

Attribute:

xmlns:android

StringType. Required. The namespace that defines the XML file, which must be "http://schemas.android.com/apk/res/android".

<item>

Define the drawable resource used by a Level

Attribute:

android:drawable

Drawable resource.Required. Reference A drawable Resource

android:maxLevel

IntegerType. The maximum level allowed by this item.

android:minLevel

IntegerType. The minimum level allowed by this item.

Example:

<?xml version="1.0" encoding="utf-8"?><level-list xmlns:android="http://schemas.android.com/apk/res/android" >    <item        android:drawable="@drawable/status_off"        android:maxLevel="0" />    <item        android:drawable="@drawable/status_on"        android:maxLevel="1" /></level-list>

When applied to a view, you can use the setlevel () or setimagelevel () method to change the level. Setlevel () valley levellistdrawable method, setimagelevel is some view Method

Refer:

• LevelListDrawable

The following describes how to use an instance:

1. Define in XML file

Level_list.xml:

<?xml version="1.0" encoding="utf-8"?><level-list xmlns:android="http://schemas.android.com/apk/res/android">  <item android:maxLevel="1" android:drawable="@drawable/image1" />  <item android:maxLevel="2" android:drawable="@drawable/image2" />  <item android:maxLevel="3" android:drawable="@drawable/image3" />  <item android:maxLevel="4" android:drawable="@drawable/image4" />  <item android:maxLevel="5" android:drawable="@drawable/image5" /> </level-list>

In the layout file main. xml:

<Imageview
Android: Id = "@ + ID/imgview"
Android: src = "@ drawable/level_list"
Android: layout_width = "wrap_content"
Android: layout_height = "wrap_content"/>

2. Use the following code:

Because the image I used is too large, it may cause memory leakage, so I did some processing.

Package COM. example. drawabletest; import android. app. activity; import android. graphics. bitmap; import android. graphics. bitmapfactory; import android. graphics. drawable. bitmapdrawable; import android. graphics. drawable. levellistdrawable; import android. OS. bundle; import android. view. menu; import android. view. view; import android. widget. button; import android. widget. imageview; import android. widget. toast; Public C Lass mainactivity extends activity {private int [] IDs = new int [] {R. drawable. image1, R. drawable. image2, R. drawable. image3, R. drawable. image4, R. drawable. image5}; @ override public void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. activity_main); Final imageview = (imageview) findviewbyid (R. id. imgview); bitmapfactory. options opts = N EW bitmapfactory. options (); opts. injustdecodebounds = true; bitmapfactory. decoderesource (getresources (), R. drawable. image1, opts); opts. insamplesize = computesamplesize (OPTs,-1,500*500); opts. injustdecodebounds = false; levellistdrawable = new levellistdrawable (); // defines a leveldrawable try {for (INT I = 0; I <IDs. length; I ++) {// For Loop, load 5 drawable resources bitmap BMP = bitmapfactory. Decoderesource (getresources (), IDS [I], opts); bitmapdrawable = new bitmapdrawable (BMP); levellistdrawable. addlevel (I, I + 1, bitmapdrawable); // Add to levellistdrawable} imageview. setimagedrawable (levellistdrawable); // set} catch (outofmemoryerror ERR) {err. printstacktrace ();} imageview. setimagelevel (1); // The default level is 0. Set it to 1 button BTN = (button) findviewbyid (R. id. BTN); BTN. setonclicklisten Er (new view. onclicklistener () {public void onclick (view v) {int I = imageview. getdrawable (). getlevel (); if (I> = 5) I = 0; // imageview. setimagelevel (++ I); // change level imageview. getdrawable (). setlevel (++ I); // achieves the same effect}) ;}@ override public Boolean oncreateoptionsmenu (menu) {getmenuinflater (). inflate (R. menu. activity_main, menu); Return true;} public static int computesamplesize (bitmapfactory. Options options, int minsidelength, int maxnumofpixels) {int initialsize = values (options, minsidelength, maxnumofpixels); int roundedsize; If (initialsize <= 8) {roundedsize = 1; while (roundedsize <initialsize) {roundedsize <= 1 ;}} else {roundedsize = (initialsize + 7)/8*8;} return roundedsize ;} private Static int computeinitialsamplesize (bitmapfactory. options op Tions, int minsidelength, int maxnumofpixels) {double W = options. outwidth; double H = options. outheight; int lowerbound = (maxnumofpixels =-1 )? 1: (INT) math. Ceil (math. SQRT (w * H/maxnumofpixels); int upperbound = (minsidelength =-1 )? 128: (INT) math. min (math. floor (W/minsidelength), math. floor (H/minsidelength); If (upperbound <lowerbound) {// return the larger one when there is no overlapping zone. return lowerbound;} If (maxnumofpixels =-1) & (minsidelength =-1) {return 1;} else if (minsidelength =-1) {return lowerbound;} else {return upperbound ;}}}

Note the following when using leveldrawable:

1. The default level is 0. If no level matches 0, it is not displayed.

2. maxlevel is preferred for level matching. That is, if there is an item, Min: 1, Max: 2. Another item, Min: 2, Max: 3.

If level = 2 is set at this time, the first item is matched.