Android Programming

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This article applies to Android only.

See also: Multiplatform Programming Guide

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See also Custom Drawn Interface/Android

Knowing general Android programming can be very useful to help develop the Lazarus Android Interface.

Platform Tips

How to...

Build the NDK OpenGL example

Just follow these steps:

Step 1 - Download and install the Android NDK, Android SDK and Ant. More information here: Android_Interface/Using_the_Android_SDK,_Emulator_and_Phones

Step 2 - Install the pre-compiled FPC cross-compiler. Instructions here: Android_Interface#Using_the_pre-compiled_compiler

Step 3 - Download the latest lazarus-ccr sourceforge code: 

svn co https://lazarus-ccr.svn.sourceforge.net/svnroot/lazarus-ccr lazarus-ccr

or if you think it is too big you can download just the folder lazarus-ccr/bindings/android-ndk

Step 4 - Building the Pascal Library

Light bulb  Note: In the steps below, the directory /home/felipe/Programas or ~/Programas is used. Please adjust if your paths are different.

Open the project lazarus-ccr/bindings/android-ndk/examples/opengltest/opengltest.lpi

Go to Project->Project Options->Paths and where is written "Libraries -Fl" you should see a value like this: 

/home/felipe/Programas/android-ndk-r5/platforms/android-9/arch-arm/usr/lib

Change it to the correct path in your system which points to the NDK and to the library folder for your minimal required Android API Level

Now build the project using Lazarus.

Step 5 - Configuring the build environment

Open the file opengltest/local.properties. Change this line to point to your SDK location: 

sdk.dir=/home/felipe/Programas/android-sdk-linux

Step 6 - Buildings the APK

Open a terminal and type these commands: 

cd lazarus-ccr/bindings/ndk/examples/opengltest/android
ant debug

The APK file will be placed in opengltest/android/bin/

Step 7 - Install the APK

In this step, if you get error messages about permissions read: Android_Interface/Using_the_Android_SDK,_Emulator_and_Phones#Recognition_of_devices_under_Linux

The command to install our APK in the phone is: 

cd opengltest/android
~/Programas/android-sdk-linux/platform-tools/adb install bin/OpenGLNDKTest-debug.apk

You should see something like: 

2395 KB/s (107299 bytes in 0.043s)
       pkg: /data/local/tmp/OpenGLNDKTest-debug.apk
Success

If you get an error message that it is already installed you can install with this command: 

~/Programas/android-sdk-linux/platform-tools/adb uninstall com.pascal.opengltest

And then you can run adb logcat to see what the log says while you start it in the phone via its newly added icon: 

~/Programas/android-sdk-linux/platform-tools/adb logcat

Read the screen metrics

First fill a TDisplayMetrics with the correct info: 

uses androidutil;

var
  MyDisplayMetrics: TDisplayMetrics;
  Str: string;
  //
  lHeight, lWidth: Integer;
  xdpi, ydpi, lScreenSize: Single;
begin
  // ..
  // Objects

  MyDisplayMetrics := TDisplayMetrics.Create;
  Activity.getWindowManager().getDefaultDisplay().getMetrics(MyDisplayMetrics);

And then you can read it from the TDisplayMetrics: 

  lHeight := MyDisplayMetrics.heightPixels();
  lWidth := MyDisplayMetrics.widthPixels();
  xdpi := MyDisplayMetrics.xdpi();
  ydpi := MyDisplayMetrics.ydpi();
  lScreenSize := sqrt(sqr(lHeight / ydpi) + sqr(lWidth / xdpi));
  ldensity := MyDisplayMetrics.density();
  ldensityDpi := MyDisplayMetrics.densityDpi();
  scaledDensity := MyDisplayMetrics.scaledDensity();

Note that lots of devices lie about the xdpi and ydpi, so don't trust the lScreenSize calculated above. Smartphones might report even 10 inches of screen size, while the correct is around 4.

Details about Android devices

Since there are so many Android devices, it can be useful to keep track of some information about them. See also in the wikipedia Comparison of Android Devices [1] and details about the processors in [2].

Smartphones

Manufacturer Model Android API Name (Build.Model) Processor Android version Multi-touch Comments
HTC Wildfire HTC Wildfire armv6 2.1=>2.2 Yes -
Sony Erricson Xperia X10 X10i armv7 1.6=>2.1 No -

Tablets

Manufacturer Model Android API Name (Build.Model) Processor Android version Multi-touch Comments
Toshiba Folio 100 Tablet TOSHIBA_FOLIO_AND_A armv7 2.2 Yes -

List of devices ordered by processor compatibility (ARMv6 vs ARMv7)

List of ARMv7 devices
Advent Vega (P10AN01) Dell Streak, Streak 7 HTC Desire HTC Desire Z (T-Mobile G2) HTC Desire HD
HTC Droid Incredible HTC EVO 4G, EVO Shift 4G HTC Glacier (T-Mobile myTouch 4G) HTC Inspire 4G HTC Nexus One
HTC Thunderbolt 4G Huawei Ideos S7 LG Optimus Z Motorola Atrix 4G Motorola Bravo
Motorola Cliq 2 - untested Motorola Defy Motorola Droid 2, Droid 2 Global Motorola Droid Pro (Motorola Pro) Motorola Droid X
Motorola Xoom POV Mobii Tegra Tablet Samsung Continuum (i400) Samsung Galaxy S (i9000, Captivate,
Fascinate, Vibrant, Epic 4G)		 Samsung Galaxy Tab
Sharp IS03 Sony Ericsson Xperia X10 Toshiba AS100 Viewsonic gTablet Acer Liquid E
Acer Liquid (Liquid A1) Archos 101 Internet Tablet Motorola Charm Motorola Droid (Milestone) Samsung Galaxy S 4G
Samsung Nexus S
List of ARMv6 processors:
Android SDK emulator Asus Garmin nuvifone A50 (T-Mobile Garminfone) Augen GENTouch 78 Tablet Coby Kyros Internet Tablet (MID7015)
Geeksphone One, Geeksphone Zero HTC Aria HTC ChaCha HTC Dream (T-Mobile G1, Android Dev Phone 1)
HTC Droid Eris HTC Espresso (T-Mobile myTouch 3G Slide) HTC Hero (T-Mobile G2 Touch) HTC Legend
HTC Magic (T-Mobile myTouch 3G, T-Mobile G1 Touch) HTC Salsa HTC Tattoo HTC Wildfire
Huawei Ascend Huawei Ideos U8150-B (T-Mobile Comet) Huawei U8110 (T-Mobile Pulse Mini) Huawei U8230
LG Ally (Apex) (LG VS740) LG GW620 (Eve, InTouch Max, LinkMe) LG Optimus, Optimus M, Optimus T, Optimus S, Optimus V

LG Vortex

LG P500 MAG iMiTO iM7 vMAG iMiTO iM7S Motorola Backflip
Motorola Citrus Motorola Cliq (MB200) Motorola Dext Motorola Devour
Motorola i1 Motorola Spice XT300 Motorola Quench XT5 XT502 Pandigital Novel
Samsung GT-S5570 Galaxy Mini Samsung i5500 Galaxy 5 (Corby) Samsung i5700 Galaxy Portal (Spica) Samsung i5800 Galaxy 3
Samsung i7500 Galaxy Samsung Intercept Samsung M900 Moment Samsung S5830 Galaxy Ace
Samsung Transform Sanyo ZIO M6000 Sony Ericsson Xperia X8 Sony Ericsson Xperia X10 Mini
Sony Ericsson Xperia X10 Mini Pro Superpad 10.2" Tablet PC Viewsonic ViewPad 7 Tablet Velocity Micro T103 Cruz tablet
Vodafone 845 ZTE Blade

Playing sounds and videos on the phones

Each phone comes with different codecs installed, which means that the native Media Player will be able to play different formats in different phones. Below is a table showing which formats play in the native Media Player of each phone:

Telephone Android webm - VP8 m4v - H.264 ogv - Theora mp4 - H.264 mov - H.264 avi - RLE mpg - MPEG-1 wmv - WM9 3gp - MPEG-4
Emulator 1.6 x x x x x x x x OK
Emulator 2.1 x x x x x x x x OK
Nexus One 2.2 x OK x OK x x x x OK
HTC Desire 1.6 x OK x OK x x x OK OK
Toshiba Folio 100 2.2 x OK x OK x x x OK OK
Xperia X10 2.1 x OK x x x x x OK OK
Xperia X8 2.2 x OK x x x x x x OK
HTC Wildfire 2.1 x OK x x x x x x OK
HTC Desire HD 2.2 x OK x OK x x x x OK
Galaxy Tab 2.2 x OK x x x x x x OK
myPhone A210 1.6 x OK x x x x x x OK
Motorola Milestone 2.1 x OK x x x x x OK ?
Milestone 2 2.2 x OK x x x x x sound-only OK

Android file system

Android recommends to use getApplicationContext().getFilesDir() to obtain the data directory for the application and this routine in my HTC Wildfire returns /data/data/<package name>

The native libraries of the application are placed in /data/data/<package>/lib

A good place where we have read and write access and we can create new files and even run files is /data/data/<package name>

Creating a new Java Android application

This info can be useful for helping implement LCL-CustomDrawn-Android

Generic instructions here: http://developer.android.com/guide/developing/other-ide.html

Showing/hiding the virtual keyboard

See here: http://android-codes-examples.blogspot.com/2011/11/show-or-hide-soft-keyboard-on-opening.html

To show it: 

InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.toggleSoftInput(InputMethodManager.SHOW_FORCED,0);

and for hiding the keyboard: 

InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(singleedittext.getWindowToken(),0);

Android JNI

Using JNI (Java Native Interface) you can call most Android SDK APIs and also other Java libraries.

Table of Java types and Pascal JNI types

All of the Java types except interfaces can be represented in JNI without problems. For each Java type there is a corresponding VM Type Signature which is utilized in routines such as javaEnvRef^^.GetMethodID. There is also the JNI native type, which is the type declared in the unit lazarus/lcl/interfaces/customdrawn/android/jni.pas and should be the type utilized in JNI code written in Pascal. The Pascal equivalent is provided just for comparison, as one should use the types from jni.pas when writing JNI code.

Java type VM signature Type in jni.pas Pascal equivalent Description
boolean Z jboolean Boolean
byte B jbyte Byte
char C jchar Word
short S jshort Shortint
int I jint Integer
long J jlong Int64
float F jfloat Single
double D jdouble Double
a class, ie: String or InputStream L<full class name> ie: Ljava/lang/String; jobject N/A
Array, ie: int[] [<type-name> ie: [I N/A
A method type (arg-types)ref-type JMethodID N/A
void V N/A procedure

Example 1: Creating a Java object and calling a Java method

Let's say that you want to make Pascal JNI code equivalent to the following Java code: 

  HttpGet javaRequest = new HttpGet();
  URI myURI = new URI("http://magnifier.sourceforge.net/");
  javaRequest.setURI(myURI);

First you need to get all Class IDs involved in the process, then get all method IDs which we will use and then make the calls. If the call has parameters, then pass it in an array. The following Pascal native code is equivalent to that Java code above: 

uses jni, customdrawnint;

var
  javaClass_HttpGet, javaClass_URI: jclass;
  javaMethod_HttpGet_new, javaMethod_HttpGet_setURI,
    javaMethod_URI_new: jmethodid;
  javaRequest, javaURI: jobject;
  javaString: jstring;
  lParams: array[0..2] of JValue;
  lNativeString: PChar;
begin
  DebugLn(':>LoadHTMLPageViaJNI');
  // First call FindClass for all required classes
  javaClass_HttpGet := javaEnvRef^^.FindClass(javaEnvRef,
    'org/apache/http/client/methods/HttpGet');
  javaClass_URI := javaEnvRef^^.FindClass(javaEnvRef,
    'java/net/URI');

  // Now all Method IDs
  DebugLn(':LoadHTMLPageViaJNI 1');
  javaMethod_HttpGet_new := javaEnvRef^^.GetMethodID(javaEnvRef, javaClass_HttpGet, '<init>', '()V');
  javaMethod_HttpGet_setURI := javaEnvRef^^.GetMethodID(javaEnvRef, javaClass_HttpGet, 'setURI', '(Ljava/net/URI;)V');
  javaMethod_URI_new := javaEnvRef^^.GetMethodID(javaEnvRef, javaClass_URI, '<init>', '(Ljava/lang/String;)V');

  // Create a new instance for the HTTP request object
  // HttpGet javaRequest = new HttpGet();
  javaRequest := javaEnvRef^^.NewObject(javaEnvRef,
    javaClass_HttpGet,
    javaMethod_HttpGet_new);

  DebugLn(':LoadHTMLPageViaJNI 4 javaRequest='+IntToHex(PtrInt(javaRequest), 8));
  // Add a URI for the request object
  // URI javaURI = new URI("http://magnifier.sourceforge.net/");
  lParams[0].l := javaEnvRef^^.NewStringUTF(javaEnvRef, 'http://magnifier.sourceforge.net');
  javaURI := javaEnvRef^^.NewObjectA(javaEnvRef,
    javaClass_URI, javaMethod_URI_new, @lParams[0]);
  javaEnvRef^^.DeleteLocalRef(javaEnvRef, lParams[0].l);
  // javaRequest.setURI(javaURI);
  lParams[0].l := javaURI;
  javaEnvRef^^.CallVoidMethodA(javaEnvRef, javaRequest,
    javaMethod_HttpGet_setURI, @lParams[0]);

Example 2: Calling a static method

Let's say that you want to call the following static method located in the Bass class: http://jerome.jouvie.free.fr/nativebass/javadoc/org/jouvieje/bass/Bass.html 

  public static native int BASS_StreamCreateFile(String file, long offset, long length, int flags);

First you need to get all Class IDs involved in the process, then get the static method ID and then make the call with the parameter in the array: 

uses jni, customdrawnint;

var
  javaClass_Bass: jclass;
  javaMethod_Bass_BASS_StreamCreateFile: jmethodid;
  javaString: jstring;
  lParams: array[0..3] of JValue;
  lRetInt: jint;
begin
  // First call FindClass for all required classes
  javaClass_Bass := javaEnvRef^^.FindClass(javaEnvRef, 'org/jouvieje/bass/Bass');

  // Now all Method IDs
  javaMethod_Bass_BASS_StreamCreateFile := javaEnvRef^^.GetStaticMethodID(javaEnvRef, javaClass_Bass, 'BASS_StreamCreateFile', '(Ljava/lang/String;JJI)I');

  // Make the call
  lParams[0].l := javaEnvRef^^.NewStringUTF(javaEnvRef, '/path/to/file');
  lParams[1].j := 0; // offset
  lParams[2].j := 200; // length
  lParams[3].i := 0; // flags
  lRetInt := javaEnvRef^^.CallStaticIntMethodA(javaEnvRef, javaClass_Bass, javaMethod_Bass_BASS_StreamCreateFile, @lParams[0]);
  javaEnvRef^^.DeleteLocalRef(javaEnvRef, lParams[0].l);

References

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