1page.title=zipalign 2parent.title=Tools 3parent.link=index.html 4@jd:body 5 6<p>zipalign is an archive alignment tool that provides important 7optimization to Android application (.apk) files. 8The purpose is to ensure that all uncompressed data starts 9with a particular alignment relative to the start of the file. Specifically, 10it causes all uncompressed data within the .apk, such as images or raw files, 11to be aligned on 4-byte boundaries. This 12allows all portions to be accessed directly with {@code mmap()} even if they 13contain binary data with alignment restrictions. 14The benefit is a reduction in the amount of RAM consumed 15when running the application.</p> 16 17<p>This tool should always be used to align your .apk file before 18distributing it to end-users. The Android build tools can handle 19this for you. When using Eclipse with the ADT plugin, the Export Wizard 20will automatically zipalign your .apk after it signs it with your private key. 21The build scripts used 22when compiling your application with Ant will also zipalign your .apk, 23as long as you have provided the path to your keystore and the key alias in 24your project {@code ant.properties} file, so that the build tools 25can sign the package first.</p> 26 27<p class="caution"><strong>Caution:</strong> zipalign must only be performed 28<strong>after</strong> the .apk file has been signed with your private key. 29If you perform zipalign before signing, then the signing procedure will undo 30the alignment. Also, do not make alterations to the aligned package. 31Alterations to the archive, such as renaming or deleting entries, will 32potentially disrupt the alignment of the modified entry and all later 33entries. And any files added to an "aligned" archive will not be aligned.</p> 34 35<p>The adjustment is made by altering the size of 36the "extra" field in the zip Local File Header sections. Existing data 37in the "extra" fields may be altered by this process.</p> 38 39<p>For more information about how to use zipalign when building your 40application, please read <a href="{@docRoot}tools/publishing/app-signing.html">Signing 41Your Application</a>.</p> 42 43 44<h3>Usage</h3> 45 46<p>To align {@code infile.apk} and save it as {@code outfile.apk}:</p> 47 48<pre>zipalign [-f] [-v] <alignment> infile.apk outfile.apk</pre> 49 50<p>To confirm the alignment of {@code existing.apk}:</p> 51 52<pre>zipalign -c -v <alignment> existing.apk</pre> 53 54<p>The {@code <alignment>} is an integer that defines the byte-alignment boundaries. 55This must always be 4 (which provides 32-bit alignment) or else it effectively 56does nothing.</p> 57 58<p>Flags:</p> 59 60<ul> 61 <li>{@code -f} : overwrite existing outfile.zip</li> 62 <li>{@code -v} : verbose output</li> 63 <li>{@code -c} : confirm the alignment of the given file</li> 64</ul> 65 66 67 68