如何将StringBuilder数组从一个Activity传递到另一个Activity？

Question

我搜索了很多SO问题，它们已经老了，在docs.oracle.com上找不到更好的解决方案，我不想将每个StringBuilder转换成字符串来传递一个字符串数组，那么如何实现呢？

Answer 1

From inside the source Activity:

Intent intent = new Intent(this, DestActivity.class);
intent.putCharSequenceArrayListExtra("strings", myStringBuilders);
startActivity(intent);

You might have to do something like new ArrayList(Arrays.asList(myStringBuilders));

Answer 2

将其转换为集合，然后将其传递给intent，然后将其转换回Array。

Answer 3

To pass an StringBuilder array you can use the putExtra of Intent, like this:

Intent it = new Intent(this, YourActivity.class);
            StringBuilder[] sbAr = new StringBuilder[4];
            sbAr[0] = new StringBuilder("Array0");
            sbAr[1] = new StringBuilder("Array1");
            it.putExtra("sbParam", sbAr);

however I do not know exactly why when you will retrieve the value in activity targets the StringBuilder array is recovered as CharSequence array.

CharSequence[] csA = (CharSequence[]) getIntent().getExtras().get("sbParam");

I hope this helps

Answer 4

The best way I've seen to pass around objects without bundling is to use an EventBus (I recommend greenrobot/EventBus ).

An EventBus can be much faster than bundling. See this article .

The only down side I can see is that if your Activity/process is destroyed because of low memory it will lose the data when it's recreated; Whereas, if you store data in a bundle, the bundle will be resupplied to the Activity when it is recreated (could be wrong here).

---

Here's how it's done:

Create a POJO to store the StringBuilder for the event:

public class SaveStringBuilderEvent {
    public StringBuilder sb;
    public SaveStringBuilderEvent(StringBuilder sb){ this.sb = sb; }
}

Create first Activity, and post a StickyEvent before starting the next Activity (a 'StickyEvent' will keep the last event in memory until it is manually removed):

public class Activity1 extends Activity {
    private StringBuilder sb;
    ...

    // Function for loading the next activity
    private void loadNextActivity(){
       EventBus.getDefault().postSticky(new SaveStringBuilderEvent(sb));
       Intent intent = new Intent(this, Activity2.class);
       startActivity(intent);
    }

    ...
}

Create Second Activity and remove the stick event from the EventBus:

public class Activity2 extends Activity {
    StringBuilder sb = EventBus.getDefault()
                           .removeStickyEvent(SaveStringBuilderEvent.class)
                           .sb;
}

---

NOTE:

Personally I think it's the most proper way to handle such a situation where you don't want to bundle an object, however there are two other, less ideal, ways to maintain the state of an object between Activity life-cycles -- you could store the StringBuilder in the Application class or in a Singleton object; however, I wouldn't recommend this because:

1. If you store it in Application class then you liter variables from all Activities into the Application.
2. In addition, since the Application/Singleton have global scope, you have to make sure to null the variable so it can get garbage collected or it will stick around for the entire lifetime of the application, just wasting memory. However, using the eventBus, the variable is only stored "globally" between the postSticky and removeStickyEvent commands, so it will get garbage collected whenever those Activities do.