How does APK implement hot update feature?

First of all, regarding the timing function, here is the implementation of android.os.CountDownTimer that comes with Android. Since this class is an abstract class, the author encapsulated a Timer inner class inside Service to implement CountDownTimer, and customized some functions according to business needs. The code of the entire Timer inner class is as follows:

private static  class Timer extends CountDownTimer {



 private int timing;

 private int interval;



 private OnTimeOutCallback callback;



 Timer(int timingSeconds, int intervalSeconds, OnTimeOutCallback callback) {

 super(timingSeconds * 1000, intervalSeconds * 1000);

 timing = timingSeconds;

 interval = intervalSeconds;

 this.callback = callback;

}



 @Override

 public void onTick(long l) {

 Logger.d(TAG, "onTick:" + l + "," + this);

}



 @Override

 public void onFinish() {

 boolean ret = false;

 if(callback != null) {

 ret = callback.onTimeOut(timing, interval);

}



 if(!ret) {

 start(); // Restart timing...

}

}



 interface OnTimeOutCallback {

 /**@return true means that the life cycle of the Timer has been processed, and the Timer should not restart the counting thread. . */

 boolean onTimeOut(int timingSeconds, int countDownIntervalSeconds);

}



} // class Timer - end.< /pre> 

In this Timer class, the timing completion event is notified through a callback, and by default, the timer will be restarted for second timing counting after the timing is over and the callback is over.

Then, an internal class is encapsulated inside the Service class, which is responsible for ordinary upgrade checks. This internal class only provides a start() method and a stop() method. At the same time, since it needs to rely on the Timer class mentioned above to count regularly, in order to receive the timing result, it is necessary to implement the interface in the Timer class. The source code framework is as follows:

private class< /span> NormalUpgradeThread implements Timer.OnTimeOutCallback {



 Timer timer;



 private void start(){

 // Start the timer according to actual business needs. 

}



 private void stop(){

 // Stop the timer according to actual business needs

}



 @Override

 public boolean onTimeOut(int timingSeconds, int countDownIntervalSeconds) {

 // Processing logic

 // Connect to the server to check for upgrade



 return false / true;

}

}

So far, Service only needs to hold this NormalUpgradeThread class object to control the background upgrade sub-thread, or start and stop the timer counter.

As for the mandatory upgrade mentioned earlier, its framework is basically the same as this one.

4. Prompt and trigger upgrade

In the function of connecting to the server to detect and upgrade, I use OkHttp directly here Open source framework to achieve.

As for the parsing and error handling of the communication transmission participation result, you have to deal with it yourself.

As for the function of prompting the new upgrade package, the author here uses the traditional way of prompting with a small red dot in the appropriate place.

When the user clicks on the corresponding small red dot, a prompt dialog box will pop up. After the user confirms it, the function of downloading a new upgrade package or directly opening the system installation program will be triggered.

As for whether to download or open the installation interface, it depends on whether the upgrade package software has been successfully downloaded in the designated download directory.

5. Download and installation

About the save location of the downloaded new upgrade package file, the author here uses The cache directory under the APK application installation directory, namely

context.getCacheDir();

In In Android, there are mainly the following five locations for APK storage files:

1, the cache directory under the program installation directory, that is, the /data directory corresponds to the package The cache directory under the name;

2, the files directory under the program installation directory is also the files directory under the corresponding package name in the /data directory;

3, sdcard directory;

4, the cache directory under the exclusive directory corresponding to the package name under the sdcard directory ;

5. The files directory under the exclusive directory corresponding to the package name in the sdcard directory;

The selection is the directory shown in item 1 above.

The reason for choosing this directory is to avoid the problem of being unable to read or write due to the different default policies of the mobile phone ROM's access to the sdcard permission of the APK. The above items 1 and 2 all have read and write permissions by default, and using them is the most compatible.

When the download and verification pass, the program will be automatically opened to install the application for installation. This function also has different implementation codes due to different system versions. The core code is as follows:

Intent intent = new< /span> Intent(Intent.ACTION_VIEW);

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N ){

 intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION|Intent.FLAG_ACTIVITY_NEW_TASK);

 Uri uri = FileProvider.getUriForFile(this, "com.unionman.locator.fileprovider", apk);

 intent.setDataAndType(uri, "application/vnd.android.package-archive");

}else{

 intent.setDataAndType(Uri.fromFile(apk),"application/vnd.android.package-archive");

}

try {

 startActivity(intent);

}catch(Exception e){

 e.printStackTrace();

}

For Android7.0 and above systems, it also requires some additional configuration. For these configurations, please refer to another blog post by the author: Android How to install APK via Java code?

6. Ordinary upgrade and mandatory upgrade

The procedures described above are all ordinary upgrade procedures.

But the so-called mandatory upgrade is basically the same as the normal upgrade. The only difference is that when a new version of the application is detected, it will be automatically downloaded in the background. Of course, you can actually choose whether to download automatically according to the network used by the user, for example, only when the user connects to the Internet via WIFI, to automatically download to avoid generating additional traffic charges for the user.

When the new version of the application is downloaded, the detection cycle will be shortened. When each detection cycle arrives, since it can detect that the currently downloaded installation package is detected, the application installation will be forced to open The program is for users to confirm the installation.

The purpose of shortening the detection cycle is to prevent users from refusing to install. When the user refuses to install, it will return to the application to continue using it. If the original detection cycle is still installed at this time, this mandatory upgrade can be considered as having no "mandatory effect". As long as the user does not want to upgrade, the user only needs to return every time the installation interface pops up to continue using the old version of the software. Therefore, we must shorten the detection cycle, and shorten it very short. For example, once every 5 seconds, the user will not be able to use it if they do not upgrade, and the purpose of mandatory upgrade can be achieved to a certain extent.

As for the mandatory upgrade code, we will not post it. Knowing the principle, it is very simple to implement.

private static class Timer extends CountDownTimer {



 private int timing;

 private int interval;



 private OnTimeOutCallback callback;



 Timer(int timingSeconds, int intervalSeconds, OnTimeOutCallback callback) {

 super(timingSeconds * 1000, intervalSeconds * 1000);

 timing = timingSeconds;

 interval = intervalSeconds;

 this.callback = callback;

}



 @Override

 public void onTick(long l) {

 Logger.d(TAG, "onTick:" + l + "," + this);

}



 @Override

 public void onFinish() {

 boolean ret = false;

 if(callback != null) {

 ret = callback.onTimeOut(timing, interval);

}



 if(!ret) {

 start(); // Restart timing...

}

}



 interface OnTimeOutCallback {

 /**@return true means that the life cycle of the Timer has been processed, and the Timer should not restart the counting thread. . */

 boolean onTimeOut(int timingSeconds, int countDownIntervalSeconds);

}



} // class Timer - end.< /pre>
private class NormalUpgradeThread implements Timer.OnTimeOutCallback {



 Timer timer;



 private void start(){

 // Start the timer according to actual business needs. 

}



 private void stop(){

 // Stop the timer according to actual business needs

}



 @Override

 public boolean onTimeOut(int timingSeconds, int countDownIntervalSeconds) {

 // Processing logic

 // Connect to the server to check for upgrade



 return false / true;

}

}

context.getCacheDir();

Intent intent = new Intent(Intent.ACTION_VIEW);

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N ){

 intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION|Intent.FLAG_ACTIVITY_NEW_TASK);

 Uri uri = FileProvider.getUriForFile(this, "com.unionman.locator.fileprovider", apk);

 intent.setDataAndType(uri, "application/vnd.android.package-archive");

}else{

 intent.setDataAndType(Uri.fromFile(apk),"application/vnd.android.package-archive");

}

try {

 startActivity(intent);

}catch(Exception e){

 e.printStackTrace();

}