我一直在尝试简单地将一个带有两个变量(字符串和位置)的类推送并读取到Firebase,但一直收到此错误。
**com.google.firebase.database.DatabaseException: Class android.location.Location does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped.
at com.google.android.gms.internal.zzeas.zze(Unknown Source:51)
at com.google.android.gms.internal.zzear.zzb(Unknown Source:772)
at com.google.android.gms.internal.zzear.zza(Unknown Source:312)
at com.google.android.gms.internal.zzear.zzb(Unknown Source:0)
at com.google.android.gms.internal.zzeas.zze(Unknown Source:209)
at com.google.android.gms.internal.zzear.zzb(Unknown Source:772)
at com.google.android.gms.internal.zzear.zza(Unknown Source:0)
at com.google.firebase.database.DataSnapshot.getValue(Unknown Source:10)
at com.example.vish.mcapp.Selection$2$1.onDataChange(Selection.java:85)
at com.google.firebase.database.zzp.onDataChange(Unknown Source:7)
at com.google.android.gms.internal.zzduz.zza(Unknown Source:13)
at com.google.android.gms.internal.zzdwu.zzbvb(Unknown Source:2)
at com.google.android.gms.internal.zzdxa.run(Unknown Source:65)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)**
我试图从 firebase 推送和读取其对象的类如下。
public class DeviceDetails {
String nickname;
Location location = new Location("Test");
DeviceDetails()
{
}
DeviceDetails(String nickname)
{
this.nickname = nickname;
location.setLatitude(0.0);
location.setLongitude(0.0);
location.setTime(new Date().getTime());
}
DeviceDetails(String nickname, Location l)
{
this.nickname = nickname;
location=l;
}
}
将数据推送到Firebase工作得很好。但是如果不遇到上面的错误,我就无法阅读它。
我为写入Firebase编写的代码是:
register.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(TextUtils.isEmpty(nickname.getText().toString()))
{
Toast.makeText(Selection.this, "Nickname can't be empty", Toast.LENGTH_SHORT).show();
return;
}
else
{
Location loc = new Location("");
loc.setLatitude(19.0);
loc.setLongitude(29.5);
loc.setTime(new Date().getTime());
DeviceDetails newDevice = new DeviceDetails(nickname.getText().toString(), loc);
mDatabase.child("Phones").child(nickname.getText().toString().trim().replaceAll("\s","")).setValue(newDevice);
}
}
});
我为从Firebase读取而编写的代码,我认为罪魁祸首是: -
retrieve.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference myRef = database.child("Phones");
myRef.child(nickToRetrieve.getText().toString().trim().replaceAll("\s", "")).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
DeviceDetails dev = dataSnapshot.getValue(DeviceDetails.class);
double latitude = dev.location.getLatitude();
double longitude = dev.location.getLongitude();
String loc = "Latitude - " + latitude + " Longitude - " + longitude;
Toast.makeText(Selection.this, loc, Toast.LENGTH_LONG).show();
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
任何帮助将不胜感激。
当 Firebase 实时数据库 SDK 反序列化来自数据库的对象时,它要求正在使用的任何对象都有一个公共的无参数构造函数,可用于实例化该对象。 对象中的字段是使用 setter 方法或直接访问公共成员来设置的。
Android 的 Location 对象没有一个公共的 no-arg 构造函数,所以 SDK 并不真正知道如何创建它的实例。 事实上,大多数序列化库都有相同的要求。 因此,与其使用 Android 的位置对象,不如使用您自己的对象,根据需要将数据复制进出。
我只是简单地自己做了一个模型——
public class RequestLocation implements Parcelable {
private double lat;
private double lon;
protected RequestLocation(Parcel in) {
lat = in.readDouble();
lon = in.readDouble();
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeDouble(lat);
dest.writeDouble(lon);
}
@Override
public int describeContents() {
return 0;
}
public static final Creator<RequestLocation> CREATOR = new Creator<>() {
@Override
public RequestLocation createFromParcel(Parcel in) {
return new RequestLocation(in);
}
@Override
public RequestLocation[] newArray(int size) {
return new RequestLocation[size];
}
};
public double getLat() {
return lat;
}
public void setLat(double lat) {
this.lat = lat;
}
public double getLon() {
return lon;
}
public void setLon(double lon) {
this.lon = lon;
}
public RequestLocation(double lat, double lon) {
this.lat = lat;
this.lon = lon;
}
public RequestLocation(){
}
}
并发布它而不是框架的位置对象。