我有一个片段是一半的图像,然后是一半的文本。ImageView可能会返回Null?
试图分配ImageView
和TextView
但它说:
可能给空
,当我运行的应用程序不运行。
我包含Java和XML文件的片段并包含mainActivity java。
片段代码:
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");
}
}
布局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代码:
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;
}
}
你问一个重复的问题。它与Android Studio无关(我很乐意编辑你的帖子:P)。在发布问题之前请始终Google,这会节省您的时间和我们的时间。 http://stackoverflow.com/questions/10697915/why-custom-image-view-s-findviewbyid-returns-null – Sufian
林特的警告是说,'findViewById()'可以返回一个'null'。这只是为了让您知道应该预期为空。在这里阅读有关它 - http://stackoverflow.com/questions/31936907/why-android-studio-has-this-nullable-thing。但你的问题是阅读本 - http://stackoverflow.com/questions/10697915/why-custom-image-view-s-findviewbyid-returns-null – Sufian