问使用intent over 2 activities传递Arraylist字符串
EN

Stack Overflow用户

提问于 2020-04-11 11:38:15

回答 1查看 55关注 0票数 0

我有3个活动，活动1是从firebase获取数据，活动2是闪屏，活动3是显示数据。我想使用intent将数据从活动1传递到活动3。但是它不起作用。如果我不使用activity 2，它可以工作，但我也想使用activity 2。

练习1从firebase获取数据

matchButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mDbref = FirebaseDatabase.getInstance().getReference();
            mkomref = mDbref.child("Students");
            string = matchKriteria.getText().toString();
            Query query = mkomp.orderByChild("Komp").equalTo(string);
            query.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    if (dataSnapshot.exists()) {
                        if(nameList.size()>0)
                            nameList.clear();

                        for (DataSnapshot data : dataSnapshot.getChildren()) {
                            nameList.add(data.child("Name").getValue(String.class));
                        }
                        Intent intent = new Intent(FirstActivity.this, LoadingActivity.class);
                        intent.putExtra("value",nameList);
                        startActivity(intent);
                    }
                }

活动2闪屏

public class LoadingActivity extends AppCompatActivity {

public static int SPLASH_TIME_OUT= 5000;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_loading);


new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {
        Intent intent =new Intent(LoadingActivity.this, ResultActivity.class);
        startActivity(intent);
        finish();

    }
},SPLASH_TIME_OUT);

练习3显示了结果

public class ResultActivity extends AppCompatActivity {


private ArrayList<String> nameList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_bedrift_match_resultat);
    Intent intent = getIntent();

    if (intent != null)
        nameList = intent.getStringArrayListExtra("value");

    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));

    if (nameList.size() > 0) {
        CustomAdapter adapter = new CustomAdapter(this, nameList);
        recyclerView.setAdapter(adapter);
    }
}

}

android-intent

android

firebase

firebase-realtime-database

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回答 1

Stack Overflow用户

回答已采纳

发布于 2020-04-11 16:06:44

我认为它不起作用是因为，在您的LoadingActivity中，您没有从FirstActivity检索数据，也没有将其发送到ResultActivity。因此，您在ResultActivity中的名称列表为空

您可以尝试这样做：

public class LoadingActivity extends AppCompatActivity {

public static int SPLASH_TIME_OUT= 5000;
private ArrayList<String> nameList = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_loading);
    if (getIntent() != null) {
        namelist.addAll(getIntent().getStringArrayListExtra("value");
    }


new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {
        Intent intent =new Intent(LoadingActivity.this, ResultActivity.class);
        intent.putExtra("value",nameList);
        startActivity(intent);
        finish();

    }
},SPLASH_TIME_OUT);