Android Command Line Tools: Everything You Need

Setting Up the Environment

Before diving into Android command line tools, setting up the environment properly is essential. This involves installing necessary tools and configuring the system.

Installing the Android SDK

1. Download the SDK: Visit the official Android developer site to download the SDK. Choose either the Android Studio installer or the standalone installer for command line development.
2. Extract the SDK: Extract the downloaded SDK to a preferred location. This directory will serve as the base for all command line operations.

Setting Environment Variables

To use command line tools efficiently, set environment variables like ANDROID_HOME and PATH.

1. ANDROID_HOME: Points to the root directory of the Android SDK. For example, if the SDK is extracted to /path/to/sdk, set ANDROID_HOME to /path/to/sdk.
2. PATH: Include paths to tools and platforms within the SDK. Add ANDROID_HOME/tools, ANDROID_HOME/platform-tools, and ANDROID_HOME/build-tools to the PATH.

Example for Unix-based systems:

sh
export ANDROID_HOME=/path/to/sdk
export PATH=$PATH:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools:$ANDROID_HOME/build-tools

For Windows, set these variables in system properties or add them to .bashrc or .profile file.

Prerequisites

Ensure the following prerequisites are installed:

• Java Development Kit (JDK): Install the latest version of the JDK.
• Debian Packages: For Debian-based systems like Ubuntu, install packages such as openjdk-11-jdk, lib32ncurses5, and lib32stdc++6.

Common Command Line Tools

The Android SDK offers several command line tools essential for development.

SDK Manager

Manage SDK packages with the SDK Manager.

• List Packages:
  sh
  sdkmanager –list

• Install a Package:
  sh
  sdkmanager "build-tools;30.0.3"

Android Debug Bridge (ADB)

ADB manages emulator instances or Android-powered devices.

• List Devices:
  sh
  adb devices

• Install APK:
  sh
  adb install /path/to/apk

AVD Manager

Create and manage Android Virtual Devices (AVDs).

• Create an AVD:
  sh
  avdmanager create avd –name my_avd –package 'system-images;android-29;default;x86'

Apk Analyzer

Analyze the composition of your APK post-build. Useful for optimizing APKs for different devices and platforms.

Lint

Scan code to identify and correct structural issues.

• Run Lint:
  sh
  lint –check Basic my_app

Retrace

Decode obfuscated stack traces to map back to original source code.

• Use Retrace:
  sh
  retrace –input /path/to/stacktrace –output /path/to/output

AAPT2

Parse, index, and compile Android resources into a binary format.

• Compile Resources:
  sh
  aapt2 compile -o output /path/to/resources

Apksigner

Sign APKs and verify signatures across platform versions.

• Sign APK:
  sh
  apksigner sign –key /path/to/key /path/to/apk

Zipalign

Optimize APK files by ensuring proper alignment for performance and security.

• Align APK:
  sh
  zipalign -p 4 /path/to/apk aligned_apk.apk

Creating an Android Application

Creating an Android application from scratch using command line tools involves several steps.

Step 1: Set Up the Directory Structure

Create a directory structure for the project.

sh
mkdir src src/com src/com/helloworld
mkdir res res/layout res/values
touch AndroidManifest.xml
touch src/com/helloworld/MainActivity.java
touch res/values/values.xml
touch res/layouts/main_activity.xml

Step 2: Create AndroidManifest.xml

Define the entry point for the application.

xml

<application android:label="@string/appname">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>
</application>

Step 3: Create MainActivity.java

Define the main activity of the application.

java
package com.helloworld;

import android.os.Bundle;
import android.app.Activity;

public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}

}

Step 4: Create values.xml

Define string resources for the application.

xml

Hello world

Step 5: Create main_activity.xml

Define the layout for the main activity.

xml

<TextView
    android:id="@+id/tv"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Hello world" />

Step 6: Build the Application

Compile the application using the d8 tool.

sh
d8 –classpath $ANDROID_HOME/platforms/android-29/android.jar
–output build/classes/com/helloworld
src/com/helloworld/MainActivity.java

Step 7: Package the Application

Package the compiled application into an APK file using aapt2.

sh
aapt2 compile -o output /path/to/resources

Step 8: Sign and Align the APK

Sign and align the APK file for better performance.

sh
apksigner sign –key /path/to/key /path/to/apk
zipalign -p 4 /path/to/apk aligned_apk.apk

Debugging Applications

Debugging is an essential part of the development process. Command line tools provide several ways to debug applications.

Using Logcat

View app and system logs to debug issues.

sh
adb logcat

Using ADB Shell

Run shell commands on the connected device to debug issues.

sh
adb shell

Mastering these tools streamlines the development process and helps produce high-quality applications efficiently. Whether seasoned or just starting out, command line tools for Android development are an essential part of any developer's toolkit.