android 常用方法

‌1 getIdentifier是安卓开发一个非常有用的方法，它属于Context类，用于根据资源的名称和类型动态获取资源的id，常用于跨模块和获取系统的资源id等。

vbnet 复制代码

/**
 * Return a resource identifier for the given resource name.  A fully
 * qualified resource name is of the form "package:type/entry".  The first
 * two components (package and type) are optional if defType and
 * defPackage, respectively, are specified here.
 * 
 * <p>Note: use of this function is discouraged.  It is much more
 * efficient to retrieve resources by identifier than by name.
 * 
 * @param name The name of the desired resource.
 * @param defType Optional default resource type to find, if "type/" is
 *                not included in the name.  Can be null to require an
 *                explicit type.
 * @param defPackage Optional default package to find, if "package:" is
 *                   not included in the name.  Can be null to require an
 *                   explicit package.
 * 
 * @return int The associated resource identifier.  Returns 0 if no such
 *         resource was found.  (0 is not a valid resource ID.)
 */
@Discouraged(message = "Use of this function is discouraged because resource reflection makes "
                     + "it harder to perform build optimizations and compile-time "
                     + "verification of code. It is much more efficient to retrieve "
                     + "resources by identifier (e.g. `R.foo.bar`) than by name (e.g. "
                     + "`getIdentifier("bar", "foo", null)`).")
public int getIdentifier(String name, String defType, String defPackage) {
    return mResourcesImpl.getIdentifier(name, defType, defPackage);
}

name：资源的名称，即在res目录下的资源文件的名称，例如"id_test" defType:资源的类型，例如drawable，layout,string等。 defPackage 资源所在的包名。如果找不到对应的资源，此方法会返回0。

ini 复制代码

val resourceId = resources.getIdentifier("id_test", "string", packageName)
if (resourceId !== 0) {
    val textString = resources.getString(resourceId)
    Log.d("zhangqing", "[onCreate] resourceId=$textString")
} else {
    // 资源不存在
    Log.d("zhangqing", "[onCreate] resourceId no found")
}

xml 复制代码

<resources>
    <string name="app_name">KotlinDemoTest</string>
    <string name="id_test">我爱安卓</string>
</resources>

另外

ini 复制代码

val getResourceName = resources.getResourceName(resourceId)
val getResourceEntryName = resources.getResourceEntryName(resourceId)
val getResourcePackageName = resources.getResourcePackageName(resourceId)
val getResourceTypeName = resources.getResourceTypeName(resourceId)

Log.d("zhangqing", "[onCreate] getResourceName=$getResourceName")
Log.d("zhangqing", "[onCreate] getResourceEntryName=$getResourceEntryName")
Log.d("zhangqing", "[onCreate] getResourcePackageName=$getResourcePackageName")
Log.d("zhangqing", "[onCreate] getResourceTypeName=$getResourceTypeName")

有时我们在一个应用程序中访问另一个应用程序的资源或上下文，这时我们需要使用createPackageContext()方法，这个方法允许我们获取其他应用的上下文，并且使用这个上下文访问其资源。