android studio CoordinatorLayout＆RecyclerView空白？

问题描述：

运行我的应用程序我得到一个空白的活动，目前我只有一个应该投影图像的列表，通过从JSON读取这些图像地址，从logcat中我可以看到地址被传递给应用程序，并记录，但不知道为什么布局没有结构化，我得到一个空白的白色屏幕。android studio CoordinatorLayout＆RecyclerView空白？

使用Genymotion - android s6 - android studio 2.1.1

MyActivity;

import java.util.ArrayList; 
    import java.util.Collection; 
    import java.util.HashMap; 
    import java.util.Map; 


    public class MainActivity extends AppCompatActivity { 

ArrayList<String> image_urls = new ArrayList<String>(); 
String[] android_image_urls = new String[image_urls.size()]; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    Firebase.setAndroidContext(this); 
    ImagesAddresses(); 
    initViews(); 

} 
public void ImagesAddresses(){ 
    Firebase ref = new Firebase("https://xxxxx.firebaseio.com/xxxxxx/xxx"); 
    ref.addValueEventListener(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot snapshot) { 
      Map<String, String> allADR = (HashMap<String, String>) snapshot.getValue(); 
      if (allADR != null) { 
       Collection<String> BlkADR = allADR.values(); 

       image_urls.addAll(BlkADR); 
       android_image_urls = image_urls.toArray(android_image_urls); 

        Log.i("myTag", image_urls.toString()); 

      } 
     } 

     @Override 
     public void onCancelled(FirebaseError firebaseError) { 

     } 
    }); 
} 

private void initViews(){ 
    RecyclerView recyclerView = (RecyclerView)findViewById(R.id.card_recycler_view); 
    recyclerView.setHasFixedSize(true); 
    RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext()); 
    recyclerView.setLayoutManager(layoutManager); 

    ArrayList androidVersion = prepareData(); 
    DataAdapter adapter = new DataAdapter(getApplicationContext(),androidVersion); 
    recyclerView.setAdapter(adapter); 

} 
private ArrayList prepareData(){ 

    ArrayList android_version = new ArrayList<>(); 
    for(int i=0;i<android_image_urls.length;i++){ 
     AndroidVersion androidVersion = new AndroidVersion(); 
     androidVersion.setAndroid_image_url(android_image_urls[i]); 
     android_version.add(androidVersion); 
    } 
    return android_version; 
} 
}

activity_main.xml;

<?xml version="1.0" encoding="utf-8"?> 
    <android.support.design.widget.CoordinatorLayout 
xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:fitsSystemWindows="true"> 
<android.support.v7.widget.RecyclerView 
    android:id="@+id/card_recycler_view" 
    android:scrollbars="vertical" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"/> 

    </android.support.design.widget.CoordinatorLayout>

DataAdapter.java;

package net.janusjanus.interactive_layout; 


import android.content.Context; 
import android.support.v7.widget.RecyclerView; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ImageView; 

import com.squareup.picasso.Picasso; 

import java.util.ArrayList; 

public class DataAdapter extends RecyclerView.Adapter<DataAdapter.ViewHolder> { 
private ArrayList<AndroidVersion> android_version; 
private Context context; 

public DataAdapter(Context context,ArrayList<AndroidVersion> android_version) { 
    this.context = context; 
    this.android_version = android_version; 

} 

@Override 
public DataAdapter.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) { 
    View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.row_layout, viewGroup, false); 
    return new ViewHolder(view); 
} 

@Override 
public void onBindViewHolder(ViewHolder viewHolder, int i) { 

    Picasso.with(context).load(android_version.get(i).getAndroid_image_url()).resize(120, 60).into(viewHolder.img_android); 
} 

@Override 
public int getItemCount() { 
    return android_version.size(); 
} 

public class ViewHolder extends RecyclerView.ViewHolder{ 
    ImageView img_android; 
    public ViewHolder(View view) { 
     super(view); 

     img_android = (ImageView)view.findViewById(R.id.img_android); 
    } 
} 
}

AndroidVersion.java;

package net.janusjanus.interactive_layout; 


public class AndroidVersion { 

private String android_image_url; 


public String getAndroid_image_url() { 
    return android_image_url; 
} 

public void setAndroid_image_url(String android_image_url) { 
    this.android_image_url = android_image_url; 
} 
}

越过错误我得到了以下;

05-15 04:19:57.942 7827-7875/net.janusjanus.interactive_layout I/OpenGLRenderer: Initialized EGL, version 1.4 
05-15 04:19:58.055 7827-7875/net.janusjanus.interactive_layout W/EGL_emulation: eglSurfaceAttrib not implemented 
05-15 04:19:58.056 7827-7875/net.janusjanus.interactive_layout W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xe7d65fe0, error=EGL_SUCCESS 
05-15 04:20:01.188 7827-7827/net.janusjanus.interactive_layout I/myTag: [http://res.cloudinary.com/xxxxx/image/xxxxxx/xxxxxx/fw88v6xu6wybamg9zzt6.jpg, http://res.cloudinary.com/xxxx/image/upload/xxxxx/xxxxdgfddd.jpg, http://res.cloudinary.com/xxxxxxx/jjjjjj/upload/xxxxxxxx/vvvghgggggg.jpg]

DataAdapter.java; 和我已经搜索到的stackoverflow为eglSurfaceAttrib没有实施

增加了模拟器的磁盘大小，实施了Gapp和其他指令，我发现在下面的帖子; Android Studio - Emulator - eglSurfaceAttrib not implemented

但仍然没有布局。

由于下面的用户建议，我将initView的初始化更改为ImageAddresses的结尾，以便它遵循检索地址的步骤，并且还记录了android_version.size（）;它返回零，因此布局仍然是空白的，但不知道如何解决这个问题，

Logcat更改后;

05-15 05:59:25.025 3473-3537/net.janusjanus.interactive_layout I/OpenGLRenderer: Initialized EGL, version 1.4 
    05-15 05:59:25.174 3473-3537/net.janusjanus.interactive_layout W/EGL_emulation: eglSurfaceAttrib not implemented 
    05-15 05:59:25.174 3473-3537/net.janusjanus.interactive_layout W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xe08c47a0, error=EGL_SUCCESS 
05-15 05:59:25.253 3473-3473/net.janusjanus.interactive_layout I/myTag: 0 
05-15 05:59:25.253 3473-3473/net.janusjanus.interactive_layout I/myTag: 0 
05-15 05:59:25.655 3473-3473/net.janusjanus.interactive_layout I/myTag: 0 
05-15 05:59:25.656 3473-3473/net.janusjanus.interactive_layout I/myTag: 0 
05-15 05:59:25.656 3473-3473/net.janusjanus.interactive_layout I/myTag: 0

显然，这个错误的原因是定时执行方法发生冲突，从而由你，我想用户runOnUiThread，这我不知道如何我的代码中正确构造的建议，到目前为止，我在我的MainActivity中尝试了以下内容;

public class MainActivity extends AppCompatActivity { 

ArrayList<String> image_urls = new ArrayList<String>(); 
String[] android_image_urls = new String[image_urls.size()]; 


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

} 
public void ImagesAddresses(){ 
    Firebase ref = new Firebase("https://xxxxx.firebaseio.com/xxxxx/xxxxx"); 
    ref.addValueEventListener(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot snapshot) { 
      Map<String, String> allADR = (HashMap<String, String>) snapshot.getValue(); 
      if (allADR != null) { 
       Collection<String> BlkADR = allADR.values(); 

       image_urls.addAll(BlkADR); 
       android_image_urls = image_urls.toArray(android_image_urls);

//私有最终字符串android_image_urls [] = android_image_urls

    Log.i("myTag", image_urls.toString()); 

       initViews(); 


      } 
     } 

     @Override 
     public void onCancelled(FirebaseError firebaseError) { 

     } 
    }); 


} 

private void initViews(){ 

    runOnUiThread(new Runnable() { 
     public void run() { 
      //Do something on UiThread 

      RecyclerView recyclerView = (RecyclerView)findViewById(R.id.card_recycler_view); 
      recyclerView.setHasFixedSize(true); 
      RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext()); 
      recyclerView.setLayoutManager(layoutManager); 

      ArrayList androidVersion = prepareData(); 
      DataAdapter adapter = new DataAdapter(getApplicationContext(),androidVersion); 
      recyclerView.setAdapter(adapter); 

     } 
    }); 


} 
private ArrayList prepareData(){ 

    ArrayList android_version = new ArrayList<>(); 
    for(int i=0;i<android_image_urls.length;i++){ 
     AndroidVersion androidVersion = new AndroidVersion(); 
     androidVersion.setAndroid_image_url(android_image_urls[i]); 
     android_version.add(androidVersion); 
    } 
    return android_version; 
}

} 但我想它是不是做了正确的方式，因为应用程序仍然崩溃 - 而我得到以下错误;

05-15 07:11:34.935 11327-11327/net.janusjanus.interactive_layout E/AndroidRuntime: FATAL EXCEPTION: main 
                       Process: net.janusjanus.interactive_layout, PID: 11327 
                       java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.widget.RecyclerView$LayoutManager.canScrollVertically()' on a null object reference 
                        at android.support.v7.widget.RecyclerView.computeVerticalScrollRange(RecyclerView.java:1654) 
                        at android.view.View.onDrawScrollBars(View.java:13924) 
                        at android.view.View.onDrawForeground(View.java:17657) 
                        at android.view.View.draw(View.java:16189) 
                        at android.support.v7.widget.RecyclerView.draw(RecyclerView.java:3097) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15174) 
                        at android.view.View.draw(View.java:15948) 
                        at android.view.ViewGroup.drawChild(ViewGroup.java:3609) 
                        at android.support.design.widget.CoordinatorLayout.drawChild(CoordinatorLayout.java:1077) 
                        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3399) 
                        at android.view.View.draw(View.java:16181) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15174) 
                        at android.view.View.draw(View.java:15948) 
                        at android.view.ViewGroup.drawChild(ViewGroup.java:3609) 
                        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3399) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15169) 
                        at android.view.View.draw(View.java:15948) 
                        at android.view.ViewGroup.drawChild(ViewGroup.java:3609) 
                        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3399) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15169) 
                        at android.view.View.draw(View.java:15948) 
                        at android.view.ViewGroup.drawChild(ViewGroup.java:3609) 
                        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3399) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15169) 
                        at android.view.View.draw(View.java:15948) 
                        at android.view.ViewGroup.drawChild(ViewGroup.java:3609) 
                        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3399) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15169) 
                        at android.view.View.draw(View.java:15948) 
                        at android.view.ViewGroup.drawChild(ViewGroup.java:3609) 
                        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3399) 
                        at android.view.View.draw(View.java:16181) 
                        at com.android.internal.policy.PhoneWindow$DecorView.draw(PhoneWindow.java:2690) 
                        at android.view.View.updateDisplayListIfDirty(View.java:15174) 
                        at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:281) 
                        at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:287) 
                        at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:322) 
                        at android.view.ViewRootImpl.draw(ViewRootImpl.java:2615) 
                        at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2434) 
                        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2067) 
                        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107) 
                        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013) 
                        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858) 
                        at android.view.Choreographer.doCallbacks(Choreographer.java:670) 
                        at android.view.Choreographer.doFrame(Choreographer.java:606) 
                        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844) 
                        at android.os.Handler.handleCallback(Handler.java:739) 
                        at android.os.Handler.dispatchMessage(Handler.java:95) 
                        at android.os.Looper.loop(Looper.java:148) 
                        at android.app.ActivityThread.main(ActivityThread.java:5417) 
                        at java.lang.reflect.Method.invoke(Native Method) 
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

@Override public int getItemCount（）{ return android_version.size（）; } android_version.size（）是什么？ returs – Haroon

@Haroon感谢您指出，它正在返回0，你可以在我发布在更新中的新logcat中看到。所以我不确定该从那里得出什么结论！？ – JanusJanus

绑定时，您的数据集为空。在应用到适配器之前检查 – Haroon

答

在ImagesAddresses();您使用Firebase从您的Web服务中检索数据，你会得到通过委托方法 onDataChange的结果。由于此方法的执行是异步的，因此在调用onDataChange之前调用initViews();，因此调用prepareData()。正如你可以形象android_image_urls仍然是空的。你需要做的就是致电initViews();onDataChange，确保initViews();运行在UI Thread上。

那么，这是我错过的重要部分，我刚刚改变了它，移动initView（）;到ImagesAddresses（）的底部;方法，仍然是空白活动，但正如Haroon在上面的评论中指出的那样，android_version.size（）;返回0？我不确定这个问题是如何发生的以及如何解决这个问题？检查出新的logcat – JanusJanus

不在ImagesAddresses的末尾。在onDataChange – Blackbelt

的最后，我先做了这个，并且应用程序崩溃了，出现了这个错误; java.lang.NullPointerException：尝试在android.support.v7.widget.RecyclerView.computeVerticalScrollRange（RecyclerView）上的null对象引用上调用虚拟方法'布尔android.support.v7.widget.RecyclerView $ LayoutManager.canScrollVertically（）'。 java：1654） – JanusJanus

android studio CoordinatorLayout＆RecyclerView空白？

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