[android] How to debug apk signed for release?

I have an apk which I've signed and uploaded to Android Market, and installed on my phone. I would like to debug this release apk (by means of Eclipse) whilst it is running on my phone. I have done this before (and remember it being with one of the Android development tools; perhaps Dalvik Debug Monitor) but unfortunately cannot remember how to do it and have been unable to find any articles online. Does anyone know how this can be done?

Note: I have set android:debuggable="true" in the manifest and have enabled USB Debugging on my phone.

I tried with the following and it's worked:

release {
            debuggable true
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }

In case of you decided the debug your apk which is already in market but not assigned to be debuggable and you do not want to publish it again. So follow the below steps;

1. Decompile the Apk with ApkTool(eg. apktool d <APK_PATH>)
2. Open the AndroidManifest.xml from decompiled files
3. Set android:debuggable="true" in application tag
4. Compile the modified source with ApkTool (eg. apktool b <MODIFIED_PATH>)
5. Debuggable apk ready(which unsigned means cannot publish store). You can debug as you wish.

Besides Manuel's way, you can still use the Manifest.

In Android Studio stable, you have to add the following 2 lines to application in the AndroidManifest file:

    android:debuggable="true"
    tools:ignore="HardcodedDebugMode"

The first one will enable debugging of signed APK, and the second one will prevent compile-time error.

After this, you can attach to the process via "Attach debugger to Android process" button.

Add the following to your app build.gradle and select the specified release build variant and run

signingConfigs {
        config {
            keyAlias 'keyalias'
            keyPassword 'keypwd'
            storeFile file('<<KEYSTORE-PATH>>.keystore')
            storePassword 'pwd'
        }
    }
    buildTypes {
      release {
          debuggable true
          signingConfig signingConfigs.config
          proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }

I know this is old question, but future references. In Android Studio with Gradle:

buildTypes {
    release {
        debuggable true
        runProguard true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
    }
}

The line debuggable true was the trick for me.

Update:

Since gradle 1.0 it's minifyEnabled instead of runProguard. Look at here