Question

我试图从我的firebase数据库中获取单个字符串。虽然我没有看到任何错误，但是当我更改数据时，它没有反映出来。我只想在firebase中在线存储一个字符串，然后再检索它。我正在为Android应用做这个。这是MainActivity的代码。请告诉我哪里出错了。

package sadboy.firebase;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

[public class MainActivity extends AppCompatActivity {][1]

private TextView title;
private DatabaseReference mFirebaseDatabase;
private FirebaseDatabase mFirebaseInstance;

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

    title = (TextView)findViewById(R.id.title);
    mFirebaseInstance = FirebaseDatabase.getInstance();

    mFirebaseDatabase = mFirebaseInstance.getReference("hey");
    mFirebaseInstance.getReference("new_title").setValue("Realtime Database");
    mFirebaseInstance.getReference("new_title").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            String appTitle = dataSnapshot.getValue(String.class);
            Log.e("Hey", appTitle);
            title.setText(appTitle);
        }

        @Override
        public void onCancelled(DatabaseError error) {
            // Failed to read value
            Log.e("Hey", "Failed to read app title value.", error.toException());
        }
    });


}
}

在此处查找项目： https://github.com/heysadboy/Firebase-Sample

Answer 1

尝试使用这种方法：

public class FooTest {

@Test
public void testFinalClass(){
    // Instantiate the class under test.
    Foo foo = new Foo();

    // Instantiate the external dependency
    FinalClass realFinalClass = new FinalClass();

    // Create mock object for the final class. 
    FinalClass mockedFinalClass = mock(FinalClass.class);

    // Provide stub for mocked object.
    when(mockedFinalClass.hello()).thenReturn("1");

    // assert
    assertEquals("0", foo.executeFinal(realFinalClass));
    assertEquals("1", foo.executeFinal(mockedFinalClass));

}

修改

我对您的布局进行了细微更改，以便更轻松地测试代码。以下是我所做的更改：

<强> activity_main.xml中

我添加了一个EditText和Button。

public class MainActivity extends AppCompatActivity { private TextView title; private DatabaseReference mFirebaseDatabase; private FirebaseDatabase mFirebaseInstance; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); title = (TextView) findViewById(R.id.title); mFirebaseInstance = FirebaseDatabase.getInstance(); mFirebaseDatabase = mFirebaseInstance.getReference(); mFirebaseDatabase.child("new_title").setValue("Realtime Database"); mFirebaseDatabase.child("new_title").addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { String appTitle = dataSnapshot.getValue().toString(); Log.e("Hey", appTitle); title.setText(appTitle); } @Override public void onCancelled(DatabaseError error) { // Failed to read value Log.e("Hey", "Failed to read app title value.", error.toException()); } }); } }

<强> MainActivity.java

点击发送按钮后，我从EditText中获取字符串并将其作为<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="sadboy.firebase.MainActivity"> <EditText android:id="@+id/et_input" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginBottom="@dimen/activity_vertical_margin" android:inputType="text" /> <Button android:id="@+id/bt_send" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="@dimen/activity_vertical_margin" android:text="SEND" /> <TextView android:id="@+id/title" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout>值存储在您的Firebase数据库中，同时收听new_title处所做的更改并显示值在TextView。

new_title

结果如下：

Answer 2

您是否在firebase控制台上确定了数据库规则？像这样改变它们：

{
  "rules": {
   ".read": true,
    ".write": true
  }
}

如何实时更新firebase数据库？

2 个答案: