上下文不能爲空

當我嘗試運行該應用程序時，LogCat中出現此錯誤。上下文不能爲空

java.lang.IllegalArgumentException：上下文不能爲空。

在班級中添加畢加索代碼時發生這種情況。

這裏是adpater.Java

它說的背景是空的，我已閱讀其他職位，但我無法找到一個解決方案。

public class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder>{ 
private List<App> mApps; 
private boolean mHorizontal; 
private boolean mPager; 
private Context mContext; 


public Adapter(Context ctx, boolean horizontal, boolean pager, List<App> apps) { 
    mHorizontal = horizontal; 
    mApps = apps; 
    mPager = pager; 
    this.mContext=ctx; 
} 



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




     if (mPager) { 
      return new ViewHolder(LayoutInflater.from(parent.getContext()) 
        .inflate(R.layout.adaper_pager, parent, false)); 
     } else { 
      return mHorizontal ? new ViewHolder(LayoutInflater.from(parent.getContext()) 
        .inflate(R.layout.adapter, parent, false)) : 
        new ViewHolder(LayoutInflater.from(parent.getContext()) 
          .inflate(R.layout.adapter_vertical, parent, false)); 
     } 
    } 

    @Override 
    public void onBindViewHolder(ViewHolder holder, int position) { 
     App app = mApps.get(position); 
     //holder.imageView.setImageResource(app.getDrawable()); 
     Picasso.with(mContext).load(app.getLink()).into(holder.imageView); 
     holder.nameTextView.setText(app.getName()); 
     holder.ratingTextView.setText(String.valueOf(app.getRating())); 

    } 

    @Override 
    public int getItemViewType(int position) { 
     return super.getItemViewType(position); 
    } 

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



    public static class ViewHolder extends RecyclerView.ViewHolder { 

     public ImageView imageView; 
     public TextView nameTextView; 
     public TextView ratingTextView; 

     public ViewHolder(View itemView) { 
      super(itemView); 
      imageView = (ImageView) itemView.findViewById(R.id.igOne); 
      nameTextView = (TextView) itemView.findViewById(R.id.nameTV); 
      ratingTextView = (TextView) itemView.findViewById(R.id.rate); 
     } 

    } 

}

請幫忙。有人說這是因爲imageView爲空。我對此毫不知情。

MainActivity

public class MainActivity extends AppCompatActivity implements Toolbar.OnMenuItemClickListener { 


    private static final String TAG = "MainActivity"; 
    private Context mContext = MainActivity.this; 
    private static final int ACTIVITY_NUM = 0; 


    public static final String ORIENTATION = "orientation"; 

    private RecyclerView mRecyclerView; 
    private boolean mHorizontal; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Log.d(TAG, "OnCreate: Starting MainActivity"); 
     setupBottomNavigationView(); 


     mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView); 
     mRecyclerView.setLayoutManager(new LinearLayoutManager(this)); 
     mRecyclerView.setHasFixedSize(true); 

     if (savedInstanceState == null) { 
      mHorizontal = true; 
     } else { 
      mHorizontal = savedInstanceState.getBoolean(ORIENTATION); 
     } 

     setupAdapter(); 

    } 


    /** 
    * Setup Bottom Navigation View 
    */ 

    private void setupBottomNavigationView() { 
     Log.d(TAG, "setupBottomNavigationView: Setting up Bottom Navigation View"); 
     BottomNavigationViewEx bottomNavigationViewEx = (BottomNavigationViewEx) findViewById(R.id.bottom_nav_bar); 
     BottomNavigationViewHelper.setupBottomNavigationView(bottomNavigationViewEx); 
     BottomNavigationViewHelper.enableNavigation(mContext, bottomNavigationViewEx); 
     Menu menu = bottomNavigationViewEx.getMenu(); 
     MenuItem menuItem = menu.getItem(ACTIVITY_NUM); 
     menuItem.setChecked(true); 


    } 

    public void click(View v) { 
     Intent mIntent = null; 
     switch (v.getId()) { 
      case R.id.serve: 
       mIntent = new Intent(this, SearchActivity.class); 
       break; 

      case R.id.imageButton2: 
       mIntent = new Intent(this, SearchActivity.class); 
       break; 
     } 
     startActivity(mIntent); 
    } 


    /////////// 

    @Override 
    protected void onSaveInstanceState(Bundle outState) { 
     super.onSaveInstanceState(outState); 
     outState.putBoolean(ORIENTATION, mHorizontal); 
    } 

    private void setupAdapter() { 
     List<App> apps = getApps(); 

     SnapAdapter snapAdapter = new SnapAdapter(); 
     if (mHorizontal) { 
      snapAdapter.addSnap(new Snap(Gravity.CENTER_HORIZONTAL, "Snap Start", apps)); 
      snapAdapter.addSnap(new Snap(Gravity.START, "Snap Middle", apps)); 
      snapAdapter.addSnap(new Snap(Gravity.END, "Snap End", apps)); 
      snapAdapter.addSnap(new Snap(Gravity.CENTER, "Pager snap", apps)); 
     } else { 
      snapAdapter.addSnap(new Snap(Gravity.CENTER_VERTICAL, "Snap center", apps)); 
      snapAdapter.addSnap(new Snap(Gravity.TOP, "Snap top", apps)); 
      snapAdapter.addSnap(new Snap(Gravity.BOTTOM, "Snap bottom", apps)); 
     } 

     mRecyclerView.setAdapter(snapAdapter); 
    } 

    private List<App> getApps() { 

     List<App> apps = new ArrayList<>(); 
     apps.add(new App("Google+", "http://uupload.ir/files/aud7_brickone.jpg", 4.6f)); 

     return apps; 
    } 

    @Override 
    public boolean onMenuItemClick(MenuItem item) { 

     return false; 
    } 


}

SnapAdapter

public class SnapAdapter extends RecyclerView.Adapter<SnapAdapter.ViewHolder> implements GravitySnapHelper.SnapListener { 

    public static final int VERTICAL = 0; 
    public static final int HORIZONTAL = 1; 
    private Context mContext; 



    private ArrayList<Snap> mSnaps; 
    // Disable touch detection for parent recyclerView if we use vertical nested recyclerViews 
    private View.OnTouchListener mTouchListener = new View.OnTouchListener() { 
     @Override 
     public boolean onTouch(View v, MotionEvent event) { 
      v.getParent().requestDisallowInterceptTouchEvent(true); 
      return false; 
     } 
    }; 

    public SnapAdapter() { 
     mSnaps = new ArrayList<>(); 
    } 

    public void addSnap(Snap snap) { 
     mSnaps.add(snap); 
    } 

    @Override 
    public int getItemViewType(int position) { 
     Snap snap = mSnaps.get(position); 
     switch (snap.getGravity()) { 
      case Gravity.CENTER_VERTICAL: 
       return VERTICAL; 
      case Gravity.CENTER_HORIZONTAL: 
       return HORIZONTAL; 
      case Gravity.START: 
       return HORIZONTAL; 
      case Gravity.TOP: 
       return VERTICAL; 
      case Gravity.END: 
       return HORIZONTAL; 
      case Gravity.BOTTOM: 
       return VERTICAL; 
     } 
     return HORIZONTAL; 
    } 

    @Override 
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     View view = viewType == VERTICAL ? LayoutInflater.from(parent.getContext()) 
       .inflate(R.layout.adapter_snap_vertical, parent, false) 
       : LayoutInflater.from(parent.getContext()) 
       .inflate(R.layout.adapter_snap, parent, false); 

     if (viewType == VERTICAL) { 
      view.findViewById(R.id.recycle_view).setOnTouchListener(mTouchListener); 
     } 

     return new ViewHolder(view); 

    } 

    @Override 
    public void onBindViewHolder(ViewHolder holder, int position) { 
     Snap snap = mSnaps.get(position); 
     holder.snapTextView.setText(snap.getText()); 

     if (snap.getGravity() == Gravity.START || snap.getGravity() == Gravity.END) { 
      holder.recyclerView.setLayoutManager(new LinearLayoutManager(holder 
        .recyclerView.getContext(), LinearLayoutManager.HORIZONTAL, false)); 
      holder.recyclerView.setOnFlingListener(null); 
      new GravitySnapHelper(snap.getGravity(), false, this).attachToRecyclerView(holder.recyclerView); 
     } else if (snap.getGravity() == Gravity.CENTER_HORIZONTAL) { 
      holder.recyclerView.setLayoutManager(new LinearLayoutManager(holder 
        .recyclerView.getContext(), snap.getGravity() == Gravity.CENTER_HORIZONTAL ? 
        LinearLayoutManager.HORIZONTAL : LinearLayoutManager.VERTICAL, false)); 
      holder.recyclerView.setOnFlingListener(null); 
      new LinearSnapHelper().attachToRecyclerView(holder.recyclerView); 
     } else if (snap.getGravity() == Gravity.CENTER) { // Pager snap 
      holder.recyclerView.setLayoutManager(new LinearLayoutManager(holder 
        .recyclerView.getContext(), LinearLayoutManager.HORIZONTAL, false)); 
      holder.recyclerView.setOnFlingListener(null); 
      new PagerSnapHelper().attachToRecyclerView(holder.recyclerView); 
     } else { // Top/Bottom 
      holder.recyclerView.setLayoutManager(new LinearLayoutManager(holder 
        .recyclerView.getContext())); 
      holder.recyclerView.setOnFlingListener(null); 
      new GravitySnapHelper(snap.getGravity()).attachToRecyclerView(holder.recyclerView); 
     } 


     holder.recyclerView.setAdapter(new Adapter(mContext, snap.getGravity() == Gravity.START 
      || snap.getGravity() == Gravity.END 
      || snap.getGravity() == Gravity.CENTER_HORIZONTAL, 
      snap.getGravity() == Gravity.CENTER, snap.getApps())); 
    } 

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

    @Override 
    public void onSnap(int position) { 
     Log.d("Snapped: ", position + ""); 
    } 

    public static class ViewHolder extends RecyclerView.ViewHolder { 

     public TextView snapTextView; 
     public RecyclerView recyclerView; 

     public ViewHolder(View itemView) { 
      super(itemView); 
      snapTextView = (TextView) itemView.findViewById(R.id.snapTextView); 
      recyclerView = (RecyclerView) itemView.findViewById(R.id.recycle_view); 
     } 

    } 
}

來源

2017-08-19 J. Doe

爲了將來的參考，1）它是LogCat，而不是CatLog（nitpick）和2）不要爲Java代碼使用片段。 JavaScript和Java不一樣。片段是僅適用於基於網頁代碼（HTML，JS，CSS） – Zoe

java.lang.IllegalArgumentException: Context must not be null.

A constructor in Java is a block of code similar to a method that's called when an instance of an object is created.

你應該通過Context

 private Context mContext; 

    public Adapter(Context ctx,boolean horizontal, boolean pager, List<App> apps) { 
     mHorizontal = horizontal; 
     mApps = apps; 
     mPager = pager; 
     this.mContext=ctx; // Call here 


}

logcat的拋出

the error is: Error:(110, 40) error: constructor Adapter in class Adapter cannot be applied to given types; required: boolean,boolean,List,Context found: boolean,boolean,List reason: actual and formal argument lists differ in length

pass值喜歡這樣

Adapter mAdapter = new Adapter (Youractivity_name.this, boolean, boolean , list);

new Adapter(Your_Activity.this, boolean, boolean , List<App>);

來源

2017-08-19 08:18:53

我這樣做，現在叫SnapAdpater另一個類得到一個錯誤： holder.recyclerView.setAdapter（新適配器（snap.getGravity（）== Gravity.START || snap.getGravity（）== Gravity.END || snap.getGravity（）== Gravity.CENTER_HORIZONTAL， snap.getGravity（）== Gravity.CENTER，snap.getApps（）））; } 錯誤是：錯誤：（110，40）錯誤：構造函數類Adapter中的Adapter不能應用於給定的類型; 要求：布爾，布爾型，列表，發現語境：布爾，布爾型，列表原因：實際的和正式的參數列表長度 –

不同@ J.Doe添加這個問題部分 –

@ J.Doe你還需要添加構造函數的上下文參數。這個錯誤是因爲你傳遞了'（Context，boolean，boolean，List ）'但構造函數仍然是'（布爾值，布爾值，列表）' – Zoe

電話適配器和改變構造函數

public Adapter(Context context ,boolean horizontal, boolean pager, List<App> apps) { 
    mHorizontal = horizontal; 
    mApps = apps; 
    mPager = pager; 
    mContext = context; 
}

來源

2017-08-19 08:19:51

上下文不能爲空

回答

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