我对Firebase是个新手。我无法从firebase检索数据

Question

   mDatabase.child("KhCm8DZpg72BBXCISCC").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                Product product = dataSnapshot.getValue(Product.class);
                     s="Product Name: "+product.getName();
                          textView.setText(s);    
    }

            @Override
            public void onCancelled(DatabaseError error) {

            }
        });

这是im用于检索的代码

        android {
                 compileSdkVersion 23
                 buildToolsVersion "25.0.2"
                defaultConfig {
               applicationId "com.example.android.supermarket"
                minSdkVersion 19
                targetSdkVersion 23
            versionCode 1
                versionName "1.0"
                 testInstrumentationRunner                                             "android.support.test.runner.AndroidJUnitRunner"
              }
            buildTypes {
             release {
                     minifyEnabled false
           proguardFiles getDefaultProguardFile('proguard-android.txt'),        'proguard-rules.pro'
    }
}
           }

                 dependencies {
         compile fileTree(dir: 'libs', include: ['*.jar'])
             androidTestCompile('com.android.support.test.espresso:espresso- core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
})

compile 'com.android.support:design:23.4.0'
compile 'com.android.support:design:23.4.0'
compile 'com.android.support:appcompat-v7:23.4.0'
compile 'com.android.support:support-v4:23.4.0'
compile 'com.google.android.gms:play-services-appindexing:9.8.0'
compile 'com.google.firebase:firebase-auth:10.0.1'
compile 'com.google.firebase:firebase-database:10.0.1'
testCompile 'junit:junit:4.12'
        }

Answer 1

mDatabase.child("products").addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                    //this loop will iterate through all the available children
                    for(DataSnapshot ds:dataSnpshot.getChildren())
                    {
                         Product product = ds.getValue(Product.class);
                         s="Product Name: "+product.getName();
                         textView.setText(s); //this would be overwritten
                    }    
        }

                @Override
                public void onCancelled(DatabaseError error) {

                }
            });