Android-将数据保存到内部存储

Question

I'm working on a simple to-do list app, and I'm trying to read/write data from/to internal storage. I'm trying to understand when exactly those read/write methods should be called.

I know that the activity class has an onCreate() method which will be a reasonable location for my read method, but where should I call my write method?

I want to call it when the app closes/ends, so I'd assume onDestory() is a good location, but i heard that onDestroy() may not be a good location for data storage operations and i should use onStop() .

Any help or ideas?

Answer 1

Following the table in the Android Developers Guide on the Activity Lifecycle , your app may be killed by the system any time without warning after either onPause() (for Pre-HONEYCOMB devices) or after onStop() . So you probably want to write your data in these methods to make sure nothing gets lost. So for newer devices (API level 11 and up), onStop() should be fine. If your app should run on older devices as well, onPause() would be the best place.

Answer 2

It depends on Application Lifecycle.

And see This .

onStop() invokes when user press home button(Hard Key).

And then, if memory insufficient or another reason, Android Memory Manager will kill your app instant and onDestory() will never called.

The best thing you have to is make a button to save datas. Of course, Include onStop() save routine.

Answer 3

This is Just sample code. But you get the idea. Create a custom method implementing the code below and call it on some events like "onClick" or any other.

File file;
    FileOutputStream strem = null;
    String line = "Hey this is my name";
    try {
        file = new File("sdcard/newFile.txt");
        strem = new FileOutputStream(file);
        byte[] bytes = line.getBytes();
        strem.write(bytes);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            strem.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }