java - 如何从 myRef.addValueEventListener 实例化一个全局变量
问题描述
使用myRef.addValueEventListener，我从 中获取一些数据firebase database，尝试将这些数据设置为全局变量，结果始终为 0。
public class EngineActivity extends AppCompatActivity implements EngineAdapter.OnDetailListener {
private RecyclerView recyclerView;
private RecyclerView.Adapter adapter;
private List<ListItem> listItems;
private TextView textViewRec;
private double count;
private double car_start;
private double count1, check_engine_light;
private double count2, coolant_leak;
private double count3, engine_noise;
private double count4, engine_oil;
private double count5, engine_stall;
private double count6, engine_temp;
private double count7, idle_rough;
private double count8, poor_fuel_economy;
private double count9, smoke_exhaust;
private double count10, vacuum_leak;
private double count11, engine_overheating;
private double sum;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_engine);
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("engine");
myRef.addValueEventListener(new ValueEventListener() {
@RequiresApi(api = Build.VERSION_CODES.N)
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
count = dataSnapshot.child("car_start").child("no_clicks").getValue(Double.class);
count1 = dataSnapshot.child("check_engine_light").child("no_clicks").getValue(Double.class);
Log.v("ankura", "Value is " + count1);
count2 = dataSnapshot.child("coolant_leak").child("no_clicks").getValue(Double.class);
count3 = dataSnapshot.child("engine_noise").child("no_clicks").getValue(Double.class);
count4 = dataSnapshot.child("engine_oil").child("no_clicks").getValue(Double.class);
count5 = dataSnapshot.child("engine_stall").child("no_clicks").getValue(Double.class);
count6 = dataSnapshot.child("engine_temp").child("no_clicks").getValue(Double.class);
count7 = dataSnapshot.child("idle_rough").child("no_clicks").getValue(Double.class);
count8 = dataSnapshot.child("poor_fuel_economy").child("no_clicks").getValue(Double.class);
count9 = dataSnapshot.child("smoke_exhaust").child("no_clicks").getValue(Double.class);
count10 = dataSnapshot.child("vacuum_leak").child("no_clicks").getValue(Double.class);
count11 = dataSnapshot.child("engine_overheating").child("no_clicks").getValue(Double.class);
sum = count + count1 + count2 + count3 + count4 + count5 + count6 + count7 + count8 + count9 + count10 + count11;
Log.v("ankura_sum", "Value is " + sum);
car_start = (count / sum) * 100;
check_engine_light = (count1 / sum) * 100;
coolant_leak = (count2 / sum) * 100;
engine_noise = (count3 / sum) * 100;
Log.v("MAINankura_engine_nois2", "Value is " + engine_noise);
engine_oil = (count4 / sum) * 100;
engine_stall = (count5 / sum) * 100;
engine_temp = (count6 / sum) * 100;
idle_rough = (count7 / sum) * 100;
poor_fuel_economy = (count8 / sum) * 100;
smoke_exhaust = (count9 / sum) * 100;
vacuum_leak = (count10 / sum) * 100;
engine_overheating = (count11 / sum) * 100;
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
listItems = new ArrayList<>();
recyclerView = findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
listItems.add(new ListItem("Check Engine Light On", "Lorem Ipsum Lorem Ipsum", check_engine_light));
listItems.add(new ListItem("Engine Oil Warning Light On", "Lorem Ipsum Lorem Ipsum", engine_oil));
listItems.add(new ListItem("Engine Temperature Warning Light On", "Lorem Ipsum Lorem Ipsum", engine_temp));
listItems.add(new ListItem("Engine Overheating", "Lorem Ipsum Lorem Ipsum", engine_overheating));
listItems.add(new ListItem("Coolant Leak", "Lorem Ipsum Lorem Ipsum", coolant_leak));
listItems.add(new ListItem("Car Won't start", "Lorem Ipsum Lorem Ipsum", car_start));
listItems.add(new ListItem("Engine Idles Rough or Misfires", "Lorem Ipsum Lorem Ipsum", idle_rough));
listItems.add(new ListItem("Engine Vacuum Leak", "Lorem Ipsum Lorem Ipsum", vacuum_leak));
listItems.add(new ListItem("Engine Stalls", "Lorem Ipsum Lorem Ipsum", engine_stall));
listItems.add(new ListItem("Poor Fuel Economy", "Lorem Ipsum Lorem Ipsum", poor_fuel_economy));
listItems.add(new ListItem("Engine Noise", "Lorem Ipsum Lorem Ipsum", engine_noise));
Log.v("ankura_engine_noise", "Value is " + engine_noise);
listItems.add(new ListItem("Smoke In Exhaust", "Lorem Ipsum Lorem Ipsum", smoke_exhaust));
adapter = new EngineAdapter(listItems, this, this);
recyclerView.setAdapter(adapter);
}
public void setText(){
}
@Override
public void OnDetailClick(int position) {
Intent intent = new Intent(this, CheckEngLightActivity.class);
intent.putExtra("selected_detail", listItems.get(position));
startActivity(intent);
}
}
例如，我期望的值是car_start = 8.33330.0