Question

应用程序崩溃了，而不是在按下按钮时从FireBase检索值。我被困在这里。

firebase中的新闻表为：

按钮代码

package com.example.madhav.schoolmanagement;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class attendanceStudent extends AppCompatActivity {

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

 //When a user presses this button,new page will be opened containing
        data of firebase
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
          Intent intent = new Intent(attendanceStudent.this,NewsActivity.class);
    startActivity(intent);
                finish();
            }
        });
    }
}

从上一页按下按钮后，它将进入该页面

package com.example.madhav.schoolmanagement;

import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.squareup.picasso.Picasso;

public class NewsActivity extends AppCompatActivity {

    private RecyclerView mPeopleRV;
    private DatabaseReference mDatabase;
    private FirebaseRecyclerAdapter<News, NewsViewHolder> mPeopleRVAdapter;

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

        setTitle("News");

此处的“新闻”将反映您在Firebase中称为数据库的内容。 mDatabase = FirebaseDatabase.getInstance（）。getReference（）。child（“ News”）; mDatabase.keepSynced（true）;

        mPeopleRV = (RecyclerView) findViewById(R.id.myRecycleView);

        DatabaseReference personsRef = FirebaseDatabase.getInstance().getReference().child("News");
        Query personsQuery = personsRef.orderByKey();

        mPeopleRV.hasFixedSize();
        mPeopleRV.setLayoutManager(new LinearLayoutManager(this));

        FirebaseRecyclerOptions personsOptions = new FirebaseRecyclerOptions.Builder<News>().setQuery(personsQuery, News.class).build();

        mPeopleRVAdapter = new FirebaseRecyclerAdapter<News, NewsViewHolder>(personsOptions) {
            @Override
            protected void onBindViewHolder(NewsViewHolder holder, final int position, final News model) {
                holder.setTitle(model.getTitle());
                holder.setDesc(model.getDesc());
                holder.setImage(getBaseContext(), model.getImage());

                holder.mView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        final String url = model.getUrl();
                        Intent intent = new Intent(getApplicationContext(), NewsWebView.class);
                        intent.putExtra("id", url);
                        startActivity(intent);
                        finish();
                    }
                });
            }

            @Override
            public NewsViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

                View view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.news_row, parent, false);

                return new NewsViewHolder(view);
            }
        };

        mPeopleRV.setAdapter(mPeopleRVAdapter);
    }

    @Override
    public void onStart() {
        super.onStart();
        mPeopleRVAdapter.startListening();
    }

    @Override
    public void onStop() {
        super.onStop();
        mPeopleRVAdapter.stopListening();


    }

    public static class NewsViewHolder extends RecyclerView.ViewHolder{
        View mView;
        public NewsViewHolder(View itemView){
            super(itemView);
            mView = itemView;
        }
        public void setTitle(String title){
            TextView post_title = (TextView)mView.findViewById(R.id.post_title);
            post_title.setText(title);
        }
        public void setDesc(String desc){
            TextView post_desc = (TextView)mView.findViewById(R.id.post_desc);
            post_desc.setText(desc);
        }
        public void setImage(Context ctx, String image){
            ImageView post_image = (ImageView) mView.findViewById(R.id.post_image);
            Picasso.with(ctx).load(image).into(post_image);
        }
    }
}

新闻类的代码

package com.example.schoolmanagement;



public class News {

    private String title;
    private String desc;
    private String image;
    private String url;

    public News(String title, String desc, String image, String url) {
        this.title = title;
        this.desc = desc;//For the description in the database
        this.image = image;//For the image in the database
        this.url = url;
    }

    public News(){

    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }
}

从数据库中获取数据时使用的代码

package com.example.madhav.schoolmanagement;

import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;

public class NewsWebView extends AppCompatActivity {

    WebView myWebView;
    private ProgressBar progressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_news_web_view);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

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

        myWebView = (WebView) findViewById(R.id.webView);
        WebSettings webSettings = myWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        Bundle b = getIntent().getExtras();
        String id = b.getString("id");
        myWebView.loadUrl(id);
        myWebView.setWebViewClient(new WebViewClient());
        myWebView.setWebViewClient(new WebViewClient(){
            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                super.onPageStarted(view, url, favicon);
                progressBar.setVisibility(View.VISIBLE);
                setTitle("Loading...");
            }

            @Override
            public void onPageFinished(WebView view, String url) {
                super.onPageFinished(view, url);
                progressBar.setVisibility(View.GONE);
                setTitle(view.getTitle());
            }
        });
    }

}

应用程序崩溃，而不是从FireBase检索值

0 个答案: