java-阅读firebase DB后如何在ListView上更改颜色和字体

概述如何处理为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CustomListAdap

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@R_572_6502@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<String> items;public Customlistadapter(Context context) {    this.context = context;    items = new ArrayList<>();}@OverrIDepublic int getCount() {    return HERO_COUNT;}@OverrIDepublic String getItem(int position) {    if (position >= 0 && position < items.size()) {        return items.get(position);    }    return "";}@OverrIDepublic long getItemID(int position) {    return 0;}@OverrIDepublic 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<String> updatedItems) {    items.clear();    items.addAll(updatedItems);    notifyDataSetChanged();}}

VIEwDatabase.java

public class VIEwDatabase extends AppCompatActivity {private static final String TAG = "VIEwDatabase";//add Firebase Database stuffprivate FirebaseDatabase mFirebaseDatabase;private FirebaseAuth mAuth;private FirebaseAuth.AuthStateListener mAuthListener;private DatabaseReference myRef;private String userID;private ListVIEw mListVIEw;@OverrIDeprotected 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 in                Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUID());                toastMessage("Successfully signed in.");            } else {                // User is signed out                Log.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<String> 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));        }    }}@OverrIDepublic voID onStart() {    super.onStart();    mAuth.addAuthStateListener(mAuthListener);}@OverrIDepublic 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

<?xml version="1.0" enCoding="utf-8"?><linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="match_parent"androID:layout_height="match_parent"androID:orIEntation="vertical"> <linearLayout    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent"    androID:orIEntation="vertical"> <TextVIEw    androID:ID="@+ID/tvUserInfo"    androID:layout_wIDth="match_parent"    androID:layout_height="wrap_content"    androID:text="User information"    androID:textAlignment="center"    androID:textcolor="@color/colorPrimaryDark"    androID:textSize="25sp"/><ListVIEw    androID:ID="@+ID/ListvIEw"    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent"/></linearLayout></linearLayout>

custom_List.xml

<?xml version="1.0" enCoding="utf-8"?><linearLayoutxmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="wrap_content"androID:layout_height="wrap_content"><TextVIEw    androID:layout_wIDth="fill_parent"    androID:layout_height="wrap_content"    androID:ID="@+ID/textVIEw"    androID:textSize="20px" androID:paddingtop="10dip" androID:paddingBottom="10dip"/></linearLayout>

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<String> 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 < items.size()) {                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);            }            //Bind vIEw content here            //Todo associate holder to tag            return mVIEw;        }        public voID updateList(List<String> 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：

<?xml version="1.0" enCoding="utf-8"?><linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"androID:layout_wIDth="match_parent"androID:layout_height="match_parent"androID:orIEntation="vertical"> <linearLayout    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent"    androID:orIEntation="vertical"> <TextVIEw    androID:ID="@+ID/tvUserInfo"    androID:layout_wIDth="match_parent"    androID:layout_height="wrap_content"    androID:text="User information"    androID:textAlignment="center"    androID:textcolor="@color/colorPrimaryDark"    androID:textSize="25sp"/><ListVIEw    androID:ID="@+ID/ListvIEw"    androID:background="@color/empty_color"    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent"/></linearLayout></linearLayout>

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

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