1<html> 2<head> 3 <title>Basic Dalvik VM Invocation</title> 4</head> 5 6<body> 7<h1>Basic Dalvik VM Invocation</h1> 8 9<p> 10On an Android device, the Dalvik virtual machine usually executes embedded 11in the Android application framework. It's also possible to run it directly, 12just as you would a virtual machine on your desktop system. 13</p><p> 14After compiling your Java language sources, convert and combine the .class 15files into a DEX file, and push that to the device. Here's a simple example: 16 17</p><p><code> 18% <font color="green">echo 'class Foo {'\</font><br> 19> <font color="green">'public static void main(String[] args) {'\</font><br> 20> <font color="green">'System.out.println("Hello, world"); }}' > Foo.java</font><br> 21% <font color="green">javac Foo.java</font><br> 22% <font color="green">dx --dex --output=foo.jar Foo.class</font><br> 23% <font color="green">adb push foo.jar /sdcard</font><br> 24% <font color="green">adb shell dalvikvm -cp /sdcard/foo.jar Foo</font><br> 25Hello, world 26</code> 27</p><p> 28The <code>-cp</code> option sets the classpath. The initial directory 29for <code>adb shell</code> may not be what you expect it to be, so it's 30usually best to specify absolute pathnames. 31 32</p><p> 33The <code>dx</code> command accepts lists of individual class files, 34directories, or Jar archives. When the <code>--output</code> filename 35ends with <code>.jar</code>, <code>.zip</code>, or <code>.apk</code>, 36a file called <code>classes.dex</code> is created and stored inside the 37archive. 38</p><p> 39Run <code>adb shell dalvikvm -help</code> to see a list of command-line 40options. 41</p><p> 42 43 44 45<h2>Using a debugger</h2> 46 47<p> 48You can debug stand-alone applications with any JDWP-compliant debugger. 49There are two basic approaches. 50</p><p> 51The first way is to connect directly through TCP. Add, to the "dalvikvm" 52invocation line above, an argument like: 53</p><p> 54<code> -agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=y</code> 55</p><p> 56This tells the VM to wait for a debugger to connect to it on TCP port 8000. 57You need to tell adb to forward local port 8000 to device port 8000: 58</p><p> 59<code>% <font color="green">adb forward tcp:8000 tcp:8000</font></code> 60</p><p> 61and then connect to it with your favorite debugger (using <code>jdb</code> 62as an example here): 63</p><p> 64<code>% <font color="green">jdb -attach localhost:8000</font></code> 65</p><p> 66When the debugger attaches, the VM will be in a suspended state. You can 67set breakpoints and then tell it to continue. 68 69 70</p><p> 71You can also connect through DDMS, like you would for an Android application. 72Add, to the "dalvikvm" command line: 73</p><p> 74<code> -agentlib:jdwp=transport=dt_android_adb,suspend=y,server=y</code> 75</p><p> 76Note the <code>transport</code> has changed, and you no longer need to 77specify a TCP port number. When your application starts, it will appear 78in DDMS, with "?" as the application name. Select it in DDMS, and connect 79to it as usual, e.g.: 80</p><p> 81<code>% <font color="green">jdb -attach localhost:8700</font></code> 82</p><p> 83Because command-line applications don't include the client-side 84DDM setup, features like thread monitoring and allocation tracking will not 85be available in DDMS. It's strictly a debugger pass-through in this mode. 86</p><p> 87See <a href="debugger.html">Dalvik Debugger Support</a> for more information 88about using debuggers with Dalvik. 89 90 91</p></p> 92<address>Copyright © 2009 The Android Open Source Project</address> 93 94</body> 95</html> 96