等待直到Firebase数据检索到数据

Question

我创建测验应用程序，并使用Firebase实时数据库为我的Android应用程序检索数据。在我的活动中，我检索所有有关我的问题，答案和选择的数据。但是我等待4到5秒钟，直到出现问题为止。

只要数据没有从数据库中完全检索出来，我想显示一个进度条。如何检查是否已完全检索所有数据，以便在加载数据后关闭进度栏？

这是mainActivity.class

public class MainActivity extends AppCompatActivity {


private TextView mScoreView;
private TextView mQuestion;

private Button mButtonChoice1, mButtonChoice2, mButtonChoice3, mButtonChoice4;

public int mScore = 0;
private int mQuestionNumber = 0;
private String mAnswer;

public static String alertTitle;

private Firebase mQuestionRef, mchoice1Ref, mChoice2Ref, mChoice3Ref, mChoice4Ref, mAnswerRef;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);




    mScoreView = (TextView)findViewById(R.id.score);
    mQuestion = (TextView)findViewById(R.id.question);

    mButtonChoice1 = (Button)findViewById(R.id.choice1);
    mButtonChoice2 = (Button)findViewById(R.id.choice2);
    mButtonChoice3 = (Button)findViewById(R.id.choice3);
    mButtonChoice4 = (Button)findViewById(R.id.choice4);

    updateQuestion();

    //button1
    mButtonChoice1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(mButtonChoice1.getText().equals(mAnswer)){
                mScore = mScore + 1;
                updateScore(mScore);
                updateQuestion();
                alertTitle = "Correct!";
                corectanswer();
            }else {
                updateQuestion();
                wrong();
                alertTitle = "Wrong!";
                wronganswer();
            }
        }
    });
    //button1

    //button2
    mButtonChoice2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(mButtonChoice2.getText().equals(mAnswer)){
                mScore = mScore + 1;
                updateScore(mScore);
                updateQuestion();
                alertTitle = "Correct!";
                corectanswer();
            }else {
                updateQuestion();
                wrong();
                alertTitle = "Wrong!";
                wronganswer();
            }
        }
    });
    //button2

    //button3
    mButtonChoice3.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(mButtonChoice3.getText().equals(mAnswer)){
                mScore = mScore + 1;
                updateScore(mScore);
                updateQuestion();
                alertTitle = "Correct!";
                corectanswer();
            }else {
                updateQuestion();
                wrong();
                alertTitle = "Wrong!";
                wronganswer();
            }
        }
    });
    //button3

    //button4
    mButtonChoice4.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(mButtonChoice4.getText().equals(mAnswer)){
                mScore = mScore + 1;
                updateScore(mScore);
                updateQuestion();
                alertTitle = "Correct!";
                corectanswer();

            }else {
                updateQuestion();
                wrong();
                alertTitle = "Wrong!";
                wronganswer();
            }
        }
    });
    //button4

}

private void wrong(){

    //Toast.makeText(MainActivity.this, "Wrong", Toast.LENGTH_SHORT).show();
}




private void updateScore(int score){
    mScoreView.setText("" + mScore);
}



private void updateQuestion() {
    mQuestionRef = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber + "/question");
    mQuestionRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String question = dataSnapshot.getValue(String.class);
            mQuestion.setText(question);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });


    mchoice1Ref = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber + "/choice1");
    mchoice1Ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String choice = dataSnapshot.getValue(String.class);
            mButtonChoice1.setText(choice);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

    mChoice2Ref = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber + "/choice2");
    mChoice2Ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String choice = dataSnapshot.getValue(String.class);
            mButtonChoice2.setText(choice);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

    mChoice3Ref = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber + "/choice3");
    mChoice3Ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String choice = dataSnapshot.getValue(String.class);
            mButtonChoice3.setText(choice);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

    mChoice4Ref = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber + "/choice4");
    mChoice4Ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String choice = dataSnapshot.getValue(String.class);
            mButtonChoice4.setText(choice);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });
    mAnswerRef = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber + "/answer");
    mAnswerRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            mAnswer = dataSnapshot.getValue(String.class);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

    if(mQuestionNumber == 4){
        corectanswer();
        wronganswer();
        Intent intent = new Intent(MainActivity.this,FinishActivity.class);
        intent.putExtra("RIGHT_ANSWER_COUNT", mScore);
        startActivity(intent);
    }else {
        mQuestionNumber++;
    }

}

public void corectanswer(){
    new AlertDialog.Builder(MainActivity.this)
            .setTitle(alertTitle)
            .setMessage(mAnswer)
            .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int i) {
                    dialog.cancel();
                }
            }).show();
}

public void wronganswer(){
    new AlertDialog.Builder(MainActivity.this)
            .setTitle(alertTitle)
            .setMessage(mAnswer)
            .setPositiveButton("Ok", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int i) {
                    dialog.cancel();
                }
            }).show();
}

}

和这个startactivity.class

import com.google.firebase.database.FirebaseDatabase;

public class StartActivity extends AppCompatActivity {

private Button mulai;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start);


        TextView label = (TextView)findViewById(R.id.quizmudah);
        label.setText("proooo");

        mulai = (Button)findViewById(R.id.mulai);
        mulai.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new `Intent(getApplicationContext(),MainActivity.class);`
                startActivity(intent);
            }
        });
  }
}

这是mathQuiz.class活动

package com.belajardatabase.www.bikinquiz3;

import android.app.Application;

import com.firebase.client.Firebase;

/**
 * Created by Iman on 7/3/2018.
 */

public class MathsQuiz extends Application {
    @Override
    public void onCreate() {
        super.onCreate();

        Firebase.setAndroidContext(this);
    }
}

Answer 1

由于您的Db结构是您拥有问题编号下的所有详细信息，因此您只需读取问题编号节点，就可以加载所有数据。

在调用更新问题之前，只需显示进度条，并在获取所有数据后将其隐藏在onDataChange中即可。

我还将侦听器从Value事件更改为Single Value事件，以便它一次从DB读取数据，否则，如果不手动删除，您的侦听器将保持连接状态。

private void updateQuestion() {


    if(mQuestionNumber == 4){
        corectanswer();
        wronganswer();
        Intent intent = new Intent(MainActivity.this,FinishActivity.class);
        intent.putExtra("RIGHT_ANSWER_COUNT", mScore);
        startActivity(intent);
    }else {
        mQuestionNumber++;
        mQuestionRef = new Firebase("https://maths-quiz-d33d7.firebaseio.com/" + mQuestionNumber );
        mQuestionRef.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String question = dataSnapshot.child("question").getValue(String.class);
                mQuestion.setText(question);
                String choice1 = dataSnapshot.child("choice1").getValue(String.class);
                mButtonChoice1.setText(choice1);
                String choice2 = dataSnapshot.child("choice2").getValue(String.class);
                mButtonChoice2.setText(choice2);

                String choice3 = dataSnapshot.child("choice3").getValue(String.class);
                mButtonChoice3.setText(choice3);

                String choice4 = dataSnapshot.child("choice4").getValue(String.class);
                mButtonChoice4.setText(choice4);

                mAnswer = dataSnapshot.getValue(String.class);
            }

            @Override
            public void onCancelled(FirebaseError firebaseError) {

            }
        });
    }

}