Java 如何使用firebase在android studio中监听更改
我很难读取firebase上的更改。我试图做的是,当启动按钮被触发时,每次更改都会显示一个对话框,上面写着:“这已经执行了。” 我尝试使用addListenerForSingleValueEvent,但似乎只有在所有子项都已更改时才会显示该对话框Java 如何使用firebase在android studio中监听更改,java,android,firebase,listener,Java,Android,Firebase,Listener,我很难读取firebase上的更改。我试图做的是,当启动按钮被触发时,每次更改都会显示一个对话框,上面写着:“这已经执行了。” 我尝试使用addListenerForSingleValueEvent,但似乎只有在所有子项都已更改时才会显示该对话框 startBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) {
startBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
currentWeek = programTrackers.get(0).getWeek();
DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("ProgramTracker")
.child(GlobalUser.getmUser().getiD())
.child(programTrackers.get(0).getProgramId());
databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
final int childCount = (int) dataSnapshot.getChildrenCount();
int count = 0;
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
ProgramTracker programTracker = snapshot.getValue(ProgramTracker.class);
if (programTracker.getProgramExerciseWeek() == currentWeek) {
programTrackChecker.add(programTracker);
}
count++;
}
if (count == childCount) {
boolean isFinished = false;
//last iteration
for (int i = 0; i < programTrackChecker.size(); i++) {
if (programTrackChecker.get(i).isProgramExerciseFinished()) {
isFinished = true;
} else
isFinished = false;
}
if (isFinished) {
AlertDialog.Builder builder = new AlertDialog.Builder(DayExerciseActivity.this);
builder.setMessage("You have already completed all exercises. Are you sure you want to do it again?");
builder.setPositiveButton("Yes", (dialogInterface, i) -> {
startActivity(new Intent(DayExerciseActivity.this, DoProgramActivity.class)
.putExtra("programTrackers", programTrackers)
.putExtra("exerciseNum", String.valueOf(0)));
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.dismiss();
}
});
builder.show();
} else
startActivity(new Intent(DayExerciseActivity.this, DoProgramActivity.class)
.putExtra("programTrackers", programTrackers)
.putExtra("exerciseNum", String.valueOf(0)));
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
startBtn.setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图){
currentWeek=programTrackers.get(0.getWeek();
DatabaseReference DatabaseReference=FirebaseDatabase.getInstance().getReference(“ProgramTracker”)
.child(GlobalUser.getmUser().getiD())
.child(programTrackers.get(0.getProgramId());
databaseReference.addListenerForSingleValueEvent(新的ValueEventListener()){
@凌驾
公共void onDataChange(DataSnapshot DataSnapshot){
final int childCount=(int)dataSnapshot.getChildrenCount();
整数计数=0;
对于(DataSnapshot快照:DataSnapshot.getChildren()){
ProgramTracker ProgramTracker=snapshot.getValue(ProgramTracker.class);
如果(programTracker.getProgramExerciseWeek()==currentWeek){
programTrackChecker.add(programTracker);
}
计数++;
}
if(count==childCount){
布尔值isFinished=false;
//最后一次迭代
对于(int i=0;i{
startActivity(新意图(DayExerciseActivity.this、DoProgramActivity.class)
.putExtra(“程序跟踪器”,程序跟踪器)
.putExtra(“exerciseNum”,String.valueOf(0));
});
setNegativeButton(“取消”,新建DialogInterface.OnClickListener()){
@凌驾
公共void onClick(DialogInterface,inti){
dialogInterface.dismise();
}
});
builder.show();
}否则
startActivity(新意图(DayExerciseActivity.this、DoProgramActivity.class)
.putExtra(“程序跟踪器”,程序跟踪器)
.putExtra(“exerciseNum”,String.valueOf(0));
}
}
@凌驾
已取消的公共void(DatabaseError DatabaseError){
}
});
您需要更改以下内容:
databaseReference.addListenerForSingleValueEvent(new ValueEventListener
为此:
databaseReference.addValueEventListener(new ValueEventListener
从文档中:
public abstract void onDataChange(DataSnapshot快照)
将使用此位置的数据快照调用此方法。每次数据更改时也将调用此方法
如果答案对您有帮助,请将其更新并标记为正确,以便其他用户知道它是有帮助的!不幸的是,它不起作用。我将其更改为addValueEventListener
addValueEventListener
将继续侦听更改,因此,如果您从控制台向数据库添加新数据,例如,它将检索新的da助教。。