ProGuard — shrinking, optimization, obfuscation, and preverification of Java bytecode.

Proguard optimizes the bytecode, removes unused codes, and obfuscates the classes, fields, methods with shorter names. Optimization operates with java bytecode. Since android runs on Dalvik bytecode which is converted from java bytecode, some optimizations usually doesn’t work well ( So you should be careful ).

The obfuscated code makes your APK difficult to reverse engineer, which is the main reason why most of the developers choose proguard.

Proguard can sometimes break your code up since it renames almost everything. Be sure to thoroughly test your app before release, especially after changing proguard config.

Prevent Obfuscation In Some Classes

Every app has some kind of data classes, models, or some important classes which they cannot be obfuscated. In such circumstances, we cannot let proguard to rename or remove any fields of those classes. It’s a safe bet to add a @Keep annotation on the whole class or methods, or a wildcard rule on

1 – @Keep Annotation:

Denotes that the annotated element should not be renamed when the code is minified at build time. This is typically used on methods and classes that are accessed only via reflection so a compiler may think that the code is unused.

  public void foo() {

Note that: This annotation is available only when using the Annotations Support Library.

2 – Using ProGuard, keep class fields with wildcard:

-keepclassmembers class** {
    public protected ;
    private *** string*;

Tips & Tricks in Proguard


“Defines whether widgets contained in this layout are baseline-aligned or not.”

By setting android:baselineAligned="false" , app prevents the layout from aligning its children’s baselines, that means app doesn’t worry about where the baseline of other elements in the layout, which increases the UI performance.

Note: By default, baselineAligned is set to true.