ArrayList在方法外填充

Question

请检查更新的代码。它是说arraylist是null，同时试图从oncreate方法获取元素。顺便说一下，我将元素添加到内部类中的arraylist中。任何帮助将不胜感激。谢谢..

private ArrayList<String> imageName;
ListView listView;
ArrayList<String> test;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    context = this;
    listView = findViewById(R.id.clipslistview);
    test = new ArrayList<>();
    credentialProvider();
    setTransferUtility();
    getAll();
    Toast.makeText(context, test.get(0)+"", Toast.LENGTH_SHORT).show();
}

Thread thread = new Thread(){
    public void run(){
        final ListObjectsV2Request req = new ListObjectsV2Request().withBucketName("bucket-1234314-**********").withStartAfter(".jpg").withMaxKeys(10);
        ListObjectsV2Result result;

        imageNames = new ArrayList<>();

        result =  amazonS3Client.listObjectsV2(req);


        for (S3ObjectSummary objectSummary :
                result.getObjectSummaries()) {
            clipNames.add(objectSummary.getKey()+"");
            Log.d("TEEEST", objectSummary.getKey());
        }
    }
};

Answer 1

试试这个

List<String> names = new ArrayList<>():

Thread thread = new Thread() {
    @Override
    public void run() {
       names.add("Hi");
       names.add("KK");
       names.add("Hello");
    }
};

thread.start();

public void lengthOflit() {
    Toast.makeText(getApplicationContext, names.size()+"", Length.SHORT).show;
}

FYI

无需使用Thread将数据添加到ArrayList中

List<String> names = new ArrayList<>():
names.add("Hi");
names.add("KK");
names.add("Hello");