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Added in API level 1

DexFile

public final class DexFile
extends Object

java.lang.Object
   ↳ dalvik.system.DexFile


Manipulates DEX files. The class is similar in principle to ZipFile. It is used primarily by class loaders.

Note we don't directly open and read the DEX file here. They're memory-mapped read-only by the VM.

Summary

Public constructors

DexFile(File file)

Opens a DEX file from a given File object.

DexFile(String fileName)

Opens a DEX file from a given filename.

Public methods

void close()

Closes the DEX file.

Enumeration<String> entries()

Enumerate the names of the classes in this DEX file.

String getName()

Gets the name of the (already opened) DEX file.

static boolean isDexOptNeeded(String fileName)

Returns true if the VM believes that the apk/jar file is out of date and should be passed through "dexopt" again.

Class loadClass(String name, ClassLoader loader)

Loads a class.

static DexFile loadDex(String sourcePathName, String outputPathName, int flags)

Open a DEX file, specifying the file in which the optimized DEX data should be written.

String toString()

Returns a string representation of the object.

Protected methods

void finalize()

Called when the class is finalized.

Inherited methods

From class java.lang.Object

Public constructors

DexFile

Added in API level 1
DexFile (File file)

Opens a DEX file from a given File object. This will usually be a ZIP/JAR file with a "classes.dex" inside. The VM will generate the name of the corresponding file in /data/dalvik-cache and open it, possibly creating or updating it first if system permissions allow. Don't pass in the name of a file in /data/dalvik-cache, as the named file is expected to be in its original (pre-dexopt) state.

Parameters
file File: the File object referencing the actual DEX file
Throws
IOException if an I/O error occurs, such as the file not being found or access rights missing for opening it

DexFile

Added in API level 1
DexFile (String fileName)

Opens a DEX file from a given filename. This will usually be a ZIP/JAR file with a "classes.dex" inside. The VM will generate the name of the corresponding file in /data/dalvik-cache and open it, possibly creating or updating it first if system permissions allow. Don't pass in the name of a file in /data/dalvik-cache, as the named file is expected to be in its original (pre-dexopt) state.

Parameters
fileName String: the filename of the DEX file
Throws
IOException if an I/O error occurs, such as the file not being found or access rights missing for opening it

Public methods

close

Added in API level 1
void close ()

Closes the DEX file.

This may not be able to release all of the resources. If classes from this DEX file are still resident, the DEX file can't be unmapped. In the case where we do not release all the resources, close is called again in the finalizer.

Throws
IOException if an I/O error occurs during closing the file, which normally should not happen

entries

Added in API level 1
Enumeration<String> entries ()

Enumerate the names of the classes in this DEX file.

Returns
Enumeration<String> an enumeration of names of classes contained in the DEX file, in the usual internal form (like "java/lang/String").

getName

Added in API level 1
String getName ()

Gets the name of the (already opened) DEX file.

Returns
String the file name

isDexOptNeeded

Added in API level 1
boolean isDexOptNeeded (String fileName)

Returns true if the VM believes that the apk/jar file is out of date and should be passed through "dexopt" again.

Parameters
fileName String: the absolute path to the apk/jar file to examine.
Returns
boolean true if dexopt should be called on the file, false otherwise.
Throws
FileNotFoundException if fileName is not readable, not a file, or not present.
IOException if fileName is not a valid apk/jar file or if problems occur while parsing it.
NullPointerException if fileName is null.

loadClass

Added in API level 1
Class loadClass (String name, 
                ClassLoader loader)

Loads a class. Returns the class on success, or a null reference on failure.

If you are not calling this from a class loader, this is most likely not going to do what you want. Use forName(String) instead.

The method does not throw ClassNotFoundException if the class isn't found because it isn't reasonable to throw exceptions wildly every time a class is not found in the first DEX file we look at.

Parameters
name String: the class name, which should look like "java/lang/String"
loader ClassLoader: the class loader that tries to load the class (in most cases the caller of the method
Returns
Class the Class object representing the class, or null if the class cannot be loaded

loadDex

Added in API level 3
DexFile loadDex (String sourcePathName, 
                String outputPathName, 
                int flags)

Open a DEX file, specifying the file in which the optimized DEX data should be written. If the optimized form exists and appears to be current, it will be used; if not, the VM will attempt to regenerate it. This is intended for use by applications that wish to download and execute DEX files outside the usual application installation mechanism. This function should not be called directly by an application; instead, use a class loader such as dalvik.system.DexClassLoader.

Parameters
sourcePathName String: Jar or APK file with "classes.dex". (May expand this to include "raw DEX" in the future.)
outputPathName String: File that will hold the optimized form of the DEX data.
flags int: Enable optional features. (Currently none defined.)
Returns
DexFile A new or previously-opened DexFile.
Throws
IOException If unable to open the source or output file.

toString

Added in API level 1
String toString ()

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Returns
String a string representation of the object.

Protected methods

finalize

Added in API level 1
void finalize ()

Called when the class is finalized. Makes sure the DEX file is closed.

Throws
IOException if an I/O error occurs during closing the file, which normally should not happen
Throwable
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