ImageView可能會返回Null？

Question

我有一個片段是一半的圖像，然後是一半的文本。

試圖分配ImageView和TextView但它說：

可能給空

，當我運行的應用程序不運行。

我包含Java和XML文件的片段幷包含mainActivity java。

片段代碼：

import android.media.Image; 
import android.os.Bundle; 
import android.provider.ContactsContract; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.ViewGroup; 
import android.view.View; 
import android.widget.TextView; 
import android.widget.ImageView; 
import android.widget.TextView; 
import org.w3c.dom.Text; 
import android.view.View; 


    public class headercode extends Fragment implements Runnable{ 

     ImageView image; 
     TextView text; 


     @Override 
     public View onCreateView(LayoutInflater inflater, ViewGroup container, 
           Bundle savedInstanceState) { 

      if(getView().findViewById(R.id.imageView) != null) 
      { 

       image = (ImageView)getView().findViewById(R.id.imageView); 

      } 
      return inflater.inflate(R.layout.frag, container, false); 
     } 

     public void run(){ 

      text.setText("Test"); 

     } 
    } 

佈局XML：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:background="#692f2f"> 
    <ImageView 
     android:layout_width="match_parent" 
     android:layout_height="300dp" /> 
    <TextView 
     android:layout_width="match_parent" 
     android:layout_height="269dp" 
     android:id="@+id/text"/> 
</LinearLayout> 

MainActivity代碼：

import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.view.View; 
import android.support.design.widget.NavigationView; 
import android.support.v4.view.GravityCompat; 
import android.support.v4.widget.DrawerLayout; 
import android.support.v7.app.ActionBarDrawerToggle; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.widget.TextView; 
import android.support.v4.app.FragmentTransaction; 
import android.support.v4.app.FragmentManager; 
import android.widget.FrameLayout; 
import android.widget.Button; 



public class MainActivity extends AppCompatActivity 
     implements NavigationView.OnNavigationItemSelectedListener { 




    Button button; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 



     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
       this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
     drawer.setDrawerListener(toggle); 
     toggle.syncState(); 



     NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
     navigationView.setNavigationItemSelectedListener(this); 

     if (findViewById(R.id.fragment) != null){ 

      headercode header = new headercode(); 
      getSupportFragmentManager().beginTransaction().add(R.id.fragment,header).commit(); 




     } 

    } 

    @Override 
    public void onBackPressed() { 
     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     if (drawer.isDrawerOpen(GravityCompat.START)) { 
      drawer.closeDrawer(GravityCompat.START); 
     } else { 
      super.onBackPressed(); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu);//This is the setting top right 
     return true; 
    } 


    @SuppressWarnings("StatementWithEmptyBody") 
    @Override 
    public boolean onNavigationItemSelected(MenuItem item) { 
     // Handle navigation view item clicks here. 
     int id = item.getItemId(); 

     if (id == R.id.Technology) { 



     } else if (id == R.id.Opinion) { 




     } else if (id == R.id.travel) { 



     } else if (id == R.id.politics) { 



     }else if(id == R.id.Home){ 



     } 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     drawer.closeDrawer(GravityCompat.START); 
     return true; 
    } 

} 

Answer 1

對於片段，你應該誇大首先你在onCreateView方法XML，你得到你的視圖，你可以找到你對應的ImageView：

View myView = inflater.inflate(R.layout.frag, container, false); 

ImageView myImage = (ImageView) myView.findViewById(R.layout.my_image); 

return myView; 

中的XML，你應該爲了添加一個ID，iamgeView得到它：

<ImageView 
     android:id="@+id/my_image" 
     android:layout_width="match_parent" 
     android:layout_height="300dp" /> 

Answer 2

試圖分配的ImageView和TextView的，但它說，可能給 零誤差，當我運行它不運行的應用程序。

這是一個皮棉警告，通知您findViewById可能會返回null。如果你的xml包含你正在尋找的id，你沒有什麼可擔心的。

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     if(getView().findViewById(R.id.imageView) != null) 

getView()返回View的onCreateView回報，因此你不能用getView()內onCreateView。覆蓋onViewCreate，而是和它的參數View執行您的通話findViewById

Answer 3

在片段首先需要infalte視圖，然後assing值，其內容

例子：

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 

View rootView = inflater.inflate(R.layout.frag, container, false); 
ImageView image = (ImageView) rootView.findViewById(R.id.imageView); 
TextView tv = (TextView) rootView.findViewById(R.id.yourTextViewId); 
tv.setText("Test"); 

// Here you will perform all the actions that you want to perform and then in the end return the view like below 

return rootView; 
}