java - Firebase 实时数据库

Question

我有一个问题 我是 Android 应用程序开发的新手。

这是我的 MainActivity.java

package com.koridevbrowser.app;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

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  implement ValueEventListener{

private TextView mText;
private WebView mWebView;
ProgressBar progressBar;
private Toolbar toolbar;


private DatabaseReference database = FirebaseDatabase.getInstance().getReference();
private DatabaseReference mconf = database.child("version");

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

    toolbar = (Toolbar) findViewById(R.id.app_bar);
    setSupportActionBar(toolbar);

    mText = (TextView) findViewById(R.id.About);

    mWebView = (WebView) findViewById(R.id.activity_main_webview);

    progressBar = (ProgressBar) findViewById(R.id.progressBar1);

    String userAgent = mWebView.getSettings().getUserAgentString();
    mWebView.getSettings().setUserAgentString(userAgent);
    WebSettings webSettings = mWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    mWebView.loadUrl("http://www.kori-developer.com");
    mWebView.setWebChromeClient(new WebChromeClient());
    mWebView.setWebViewClient(new HelloWebViewClient());

}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu_main, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(final MenuItem item) {
    switch (item.getItemId()) {
        case R.id.home:
            mWebView.loadUrl("http://kori-developer.com/");
            return true;
        case R.id.KoriFiles:
            mWebView.loadUrl("http://kori-developer.com/forum/11-koridev-releases/");
            return true;
        case R.id.KoriRules:
            mWebView.loadUrl("http://kori-developer.com/forum/26-foren-regeln/");
            return true;
        case R.id.KoriDonate:
            mWebView.loadUrl("http://kori-developer.com/store/");
            return true;
        case R.id.KoriContact:
            mWebView.loadUrl("http://kori-developer.com/contact/");
            return true;
        case R.id.KoriAbout:
            Toast.makeText(MainActivity.this, "Version: 0.3b", Toast.LENGTH_LONG).show();

            return true;
        default:
            return super.onOptionsItemSelected(item);


    }
}

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    if (dataSnapshot.getValue(String.class) !=null) {
        String value = dataSnapshot.getKey();
        if(value.equals("version")) {
            String text = dataSnapshot.getValue(String.class);
            mText.setText(text);
        }
    }

}

@Override
public void onCancelled(DatabaseError databaseError) {

}


private class HelloWebViewClient extends WebViewClient{


    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {
        // TODO Auto-generated method stub
        super.onPageStarted(view, url, favicon);
    }

    @Override
    public boolean shouldOverrideUrlLoading(WebView webView, String url)
    {
        webView.loadUrl(url);
        return true;
    }

    @Override
    public void onPageFinished(WebView view, String url) {
        // TODO Auto-generated method stub
        super.onPageFinished(view, url);

        progressBar.setVisibility(view.GONE);
    }

}


@Override
public boolean onKeyDown(int keyCode, KeyEvent event) { //if back key is pressed
    if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
        mWebView.goBack();
        return true;

    }

    return super.onKeyDown(keyCode, event);

}

public void onBackPressed() {
    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
            MainActivity.this);

    // set title
    alertDialogBuilder.setTitle("Exit");

    // set dialog message
    alertDialogBuilder
            .setMessage("Do you really want to exit KoriDev?")
            .setCancelable(false)
            .setPositiveButton("Yes",new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog,int id) {
                    // if this button is clicked, close
                    // current activity
                    MainActivity.this.finish();
                }
            })
            .setNegativeButton("No",new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog,int id) {
                    // if this button is clicked, just close
                    // the dialog box and do nothing
                    dialog.cancel();
                }
            });

    // create alert dialog
    AlertDialog alertDialog = alertDialogBuilder.create();

    // show it
    alertDialog.show();

}

我会在这里尝试从实时数据库中读取版本:

case R.id.KoriAbout:
            Toast.makeText(MainActivity.this, "Version: 0.3b", Toast.LENGTH_LONG).show();

但我不知道如何使用 Firebase 的实时数据库进行设置。

我数据库中的一张图片:

Answer 1

默认是实时的……我相信。如果您在 firebase 中更改它，它会在您的应用程序中更改它。但是，对于你所拥有的，你已经将它硬编码到你的 toast 中。

你需要做这样的事情:

FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("version");

// Read from the database
myRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        // This method is called once with the initial value and again
        // whenever data at this location is updated.
        String value = dataSnapshot.getValue(String.class);
        Log.d(TAG, "Value is: " + value);
    }

    @Override
    public void onCancelled(DatabaseError error) {
        // Failed to read value
        Log.w(TAG, "Failed to read value.", error.toException());
    }
});

在这里查看他们的文档: https://firebase.google.com/docs/database/android/start/