java阅读firebaseDB后如何在ListView上更改颜色和字体

如何处理为ListView显示空视图的问题,因为当我从Firebase数据库读取数据并将其显示在ListView中时,我不知道要放入哪些数据.我正在使用CustomListAdapter更改字体颜色和ListView的背景颜色

注意：我正在从Firebase数据库读取数据,并将其显示在ListView中,任何解决方案

CustomListAdapter.java

public class CustomListAdapter extends BaseAdapter {
private static final int HERO_COUNT = 12;
private Context context;
private List items;
public CustomListAdapter(Context context) {
this.cOntext= context;
items = new ArrayList<>();
}
@Override
public int getCount() {
return HERO_COUNT;
}
@Override
public String getItem(int position) {
if (position >= 0 && position return items.get(position);
}
return "";
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View v, ViewGroup parent) {
View mView = v;
if (mView == null) {
LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mView = vi.inflate(R.layout.custom_list, null, false);
TextView text = (TextView) mView.findViewById(R.id.textView);
//textView.setTextColor(Color.BLUE);
text.setText(getItem(position));
if (items.isEmpty()) {
// Set holder color
} else {
text.setTextColor(Color.WHITE);
int color = Color.argb(200, 255, 64, 64);
text.setBackgroundColor(color);
}
}
return mView;
}
public void updateList(List updatedItems) {
items.clear();
items.addAll(updatedItems);
notifyDataSetChanged();
}
}


ViewDatabase.java

public class ViewDatabase extends AppCompatActivity {
private static final String TAG = "ViewDatabase";
//add Firebase Database stuff
private FirebaseDatabase mFirebaseDatabase;
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
private DatabaseReference myRef;
private String userID;
private ListView mListView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_database_layout);
mListView = (ListView) findViewById(R.id.listview);
CustomListAdapter adapter = new CustomListAdapter(this);
mListView.setAdapter(adapter);
//declare the database reference object. This is what we use to access the database.
//NOTE: Unless you are signed in, this will not be useable.
mAuth = FirebaseAuth.getInstance();
mFirebaseDatabase = FirebaseDatabase.getInstance();
myRef = mFirebaseDatabase.getReference();
FirebaseUser user = mAuth.getCurrentUser();
// userID = user.getUid();
userID = "";
mAuthListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = firebaseAuth.getCurrentUser();
if (user != null) {// User is signed inLog.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());toastMessage("Successfully signed in.");
} else {// User is signed outLog.d(TAG, "onAuthStateChanged:signed_out");toastMessage("Successfully signed out.");
}
// ...
}
};
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
showData(dataSnapshot);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void showData(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
DailyInfo uInfo = new DailyInfo();
uInfo.setHero1(ds.child(userID).getValue(DailyInfo.class).getHero1()); //set the name1
uInfo.setHero2(ds.child(userID).getValue(DailyInfo.class).getHero2()); //set the name2
uInfo.setHero3(ds.child(userID).getValue(DailyInfo.class).getHero3()); //set the name3
uInfo.setHero4(ds.child(userID).getValue(DailyInfo.class).getHero4()); //set the name4
uInfo.setHero5(ds.child(userID).getValue(DailyInfo.class).getHero5()); //set the name5
uInfo.setHero6(ds.child(userID).getValue(DailyInfo.class).getHero6()); //set the name6
uInfo.setHero7(ds.child(userID).getValue(DailyInfo.class).getHero7()); //set the name7
uInfo.setHero8(ds.child(userID).getValue(DailyInfo.class).getHero8()); //set the name8
uInfo.setHero9(ds.child(userID).getValue(DailyInfo.class).getHero9()); //set the name9
uInfo.setHero10(ds.child(userID).getValue(DailyInfo.class).getHero10()); //set the name10
uInfo.setHero11(ds.child(userID).getValue(DailyInfo.class).getHero11()); //set the name11
uInfo.setHero12(ds.child(userID).getValue(DailyInfo.class).getHero12()); //set the name12
//display all the information
Log.d(TAG, "showData: Hero1: " + uInfo.getHero1());
Log.d(TAG, "showData: Hero2: " + uInfo.getHero2());
Log.d(TAG, "showData: Hero3: " + uInfo.getHero3());
Log.d(TAG, "showData: Hero4: " + uInfo.getHero4());
Log.d(TAG, "showData: Hero5: " + uInfo.getHero5());
Log.d(TAG, "showData: Hero6: " + uInfo.getHero6());
Log.d(TAG, "showData: Hero7: " + uInfo.getHero7());
Log.d(TAG, "showData: Hero8: " + uInfo.getHero8());
Log.d(TAG, "showData: Hero9: " + uInfo.getHero9());
Log.d(TAG, "showData: Hero10: " + uInfo.getHero10());
Log.d(TAG, "showData: Hero11: " + uInfo.getHero11());
Log.d(TAG, "showData: Hero12: " + uInfo.getHero12());
ArrayList array = new ArrayList<>();
array.add(uInfo.getHero1());
array.add(uInfo.getHero2());
array.add(uInfo.getHero3());
array.add(uInfo.getHero4());
array.add(uInfo.getHero5());
array.add(uInfo.getHero6());
array.add(uInfo.getHero7());
array.add(uInfo.getHero8());
array.add(uInfo.getHero9());
array.add(uInfo.getHero10());
array.add(uInfo.getHero11());
array.add(uInfo.getHero12());
/* ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,array);
mListView.setAdapter(adapter);*/
if (mListView.getAdapter() instanceof CustomListAdapter) {
((CustomListAdapter) mListView.getAdapter()).updateList(array);
mListView.setBackgroundColor(ContextCompat.getColor(mListView.getContext(), R.color.category_colors));
}
}
}
@Override
public void onStart() {
super.onStart();
mAuth.addAuthStateListener(mAuthListener);
}
@Override
public void onStop() {
super.onStop();
if (mAuthListener != null) {
mAuth.removeAuthStateListener(mAuthListener);
}
}
/**
* customizable toast
*
* @param message
*/
private void toastMessage(String message) {
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
}
}


view_database_layout.xml


android:layout_
android:layout_
android:orientation="vertical">
android:layout_
android:layout_
android:orientation="vertical">
android:id="@+id/tvUserInfo"
android:layout_
android:layout_
android:text="User Information"
android:textAlignment="center"
android:textColor="@color/colorPrimaryDark"
android:textSize="25sp"/>
android:id="@+id/listview"
android:layout_
android:layout_/>




custom_list.xml


xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_
android:layout_>
android:layout_
android:layout_
android:id="@+id/textView"
android:textSize="20px" android:paddingTop="10dip" android:paddingBottom="10dip"/>



DailyInfo.java

public class DailyInfo {
private String hero1;
private String hero2;
private String hero3;
private String hero4;
private String hero5;
private String hero6;
private String hero7;
private String hero8;
private String hero9;
private String hero10;
private String hero11;
private String hero12;
public DailyInfo(){
}
public String getHero1() {
return hero1;
}
public void setHero1(String hero1) {
this.hero1 = hero1;
}
public String getHero2() {
return hero2;
}
public void setHero2(String hero2) {
this.hero2 = hero2;
}
public String getHero3() {
return hero3;
}
public void setHero3(String hero3) {
this.hero3 = hero3;
}
public String getHero4() {
return hero4;
}
public void setHero4(String hero4) {
this.hero4 = hero4;
}
public String getHero5() {
return hero5;
}
public void setHero5(String hero5) {
this.hero5 = hero5;
}
public String getHero6() {
return hero6;
}
public void setHero6(String hero6) {
this.hero6 = hero6;
}
public String getHero7() {
return hero7;
}
public void setHero7(String hero7) {
this.hero7 = hero7;
}
public String getHero8() {
return hero8;
}
public void setHero8(String hero8) {
this.hero8 = hero8;
}
public String getHero9() {
return hero9;
}
public void setHero9(String hero9) {
this.hero9 = hero9;
}
public String getHero10() {
return hero10;
}
public void setHero10(String hero10) {
this.hero10 = hero10;
}
public String getHero11() {
return hero11;
}
public void setHero11(String hero11) {
this.hero11 = hero11;
}
public String getHero12() {
return hero12;
}
public void setHero12(String hero12) {
this.hero12 = hero12;
}
}


解决方法:

您在ValueEventListener上收到响应后创建适配器：

CustomListAdapter adapter = new CustomListAdapter(ViewDatabase.this , R.layout.custom_list , mList);
ListView mListView= findViewById(R.id.listview);
mListView.setAdapter(adapter);


取而代之的是,例如,在onCreate内的ViewDatabase上设置适配器,并根据该初始状态设置颜色.

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_database_layout);
mListView = findViewById(R.id.listview);
CustomListAdapter adapter = new CustomListAdapter(this);
mListView.setAdapter(adapter);
//[...]
}


并且,而不是创建适配器,而是对其进行更新：

private void showData(DataSnapshot dataSnapshot) {
//[...]
if (mListView.getAdapter() instanceof CustomListAdapter) {
((CustomListAdapter)mListView.getAdapter()).updateList(array);
}
}


您还可以将ArrayAdapter替换为BaseAdapter作为扩展类：

public class CustomListAdapter extends BaseAdapter {
private static final int HERO_COUNT = 12;
private Context context;
private List items;
public CustomListAdapter(Context context) {
this.cOntext= context;
items = new ArrayList<>();
}
@Override
public int getCount() {
return HERO_COUNT;
}
@Override
public String getItem(int position) {
if (position >= 0 && position }
return "";
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View v, ViewGroup parent) {
View mView = v;
if (mView == null) {LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);mView = vi.inflate(R.layout.custom_list, null, false);
}
//Bind view content here
//TODO associate holder to tag
return mView;
}
public void updateList(List updatedItems) {
items.clear();
items.addAll(updatedItems);
notifyDataSetChanged();
}
}
}


编辑：

为了在接收值时更改列表上的默认背景色,可以在主布局上设置默认颜色：


android:layout_
android:layout_
android:orientation="vertical">
android:layout_
android:layout_
android:orientation="vertical">
android:id="@+id/tvUserInfo"
android:layout_
android:layout_
android:text="User Information"
android:textAlignment="center"
android:textColor="@color/colorPrimaryDark"
android:textSize="25sp"/>
android:id="@+id/listview"
android:background="@color/empty_color"
android:layout_
android:layout_/>




然后在收到值时更改它：

private void showData(DataSnapshot dataSnapshot) {
//[...]
if (mListView.getAdapter() instanceof CustomListAdapter) {
((CustomListAdapter)mListView.getAdapter()).updateList(array);
listView.setBackgroundColor(ContextCompat.getColor(listView.getContext(), R.color.loaded_color));
}
}


如果要更改行颜色,则需要在字符串为空时更改getView上的行布局.

编辑2
指定在何处进行视图更改