问题
The problem is, no matter where or how I call for this layout's components, they always return null.
setView(inflater.inflate(R.layout.search_layout, null))
This works fine. It displays the layout inside the Dialog, yet, the children are always returned as null by findViewById(R.id.some_search_layout_children).
I've tried cleaning my project multiple times, tried to implement another class for my Dialog, called findViewById() as a member of my main Activity, inside the initSearch() method, and inside an anonymous implementation of OnClickListener for the Dialog, but all with the same result. I've also tried breaking the children out into independent Views and programmatically calling them:
TextView text = (TextView) findResourceById(R.id.new_independant_textview);
But, again, the same result.
This is the relevant code:
public class Xyz extends Activity {
public void onCreate(...) { // some listener will trigger initSearch() }
private void initSearch() {
AlertDialog.Builder searchDialog = new AlertDialog.Builder(this);
LayoutInflater inflater = this.getLayoutInflater();
searchDialog.setTitle("Search Photos");
searchDialog.setMessage("Specify tag and value...");
// R.layout.search_dialog is my custom layour, it displays fine, it works.
searchDialog.setView(inflater.inflate(R.layout.search_dialog, null));
EditText tagText = (EdiText) findViewById(R.id.tagField); // WILL RETURN NULL
searchDialog.setPositiveButton( ... ) ...
searchDialog.show();
}
This line:
EditText text = (EditText) findViewById(R.id.tagField);
always returns null, no matter how or where it's called – globally, local final, etc. – it just returns null.
Here is the XML of my custom Dialog layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/search_dialog"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="@+id/tagText"
android:padding="7dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="14sp"
android:text="@string/tag" />
<EditText
android:id="@+id/tagField"
android:padding="7dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="text"/>
<TextView
android:id="@+id/valueText"
android:padding="7dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="14sp"
android:text="@string/value" />
<EditText
android:id="@+id/valueField"
android:padding="7dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="text"/>
</LinearLayout>
This is my R.java file:
public static final class id {
public static final int action_settings=0x7f0a0011;
public static final int add_album=0x7f0a0001;
public static final int add_photo=0x7f0a000d;
public static final int albums_list=0x7f0a0003;
public static final int delete_album=0x7f0a000b;
public static final int exit_finder=0x7f0a000f;
public static final int new_directory=0x7f0a000e;
public static final int open_album=0x7f0a000a;
public static final int photos_grid=0x7f0a0000;
public static final int rename_album=0x7f0a000c;
public static final int search_dialog=0x7f0a0004;
public static final int search_icon=0x7f0a0002;
public static final int splash_rutgers=0x7f0a0009;
public static final int tagField=0x7f0a0006; // problematic
public static final int tagText=0x7f0a0005; / problematic
public static final int terminate_app=0x7f0a0010;
public static final int valueField=0x7f0a0008; // problematic
public static final int valueText=0x7f0a0007; // problematic
}
回答1:
Calling findViewById() will search for views within your Activity's layout and not your dialog's view. You need to call findViewById() on the specific View that you set as your dialog's layout.
Try this
private void initSearch() {
AlertDialog.Builder searchDialog = new AlertDialog.Builder(this);
LayoutInflater inflater = this.getLayoutInflater();
searchDialog.setTitle("Search Photos");
searchDialog.setMessage("Specify tag and value...");
// R.layout.search_dialog is my custom layour, it displays fine, it works.
View dialogView = inflater.inflate(R.layout.search_dialog, null);
searchDialog.setView(dialogView);
EditText tagText = (EdiText) dialogView.findViewById(R.id.tagField);
searchDialog.setPositiveButton( ... ) ...
AlertDialog myAlert = searchDialog.create(); //returns an AlertDialog from a Builder.
myAlert.show();
}
Notice how I'm inflating the view and storing it in a View named dialogView. Then, to find your EditText named tagField, I'm using dialogView.findViewById(R.id.tagField);
回答2:
The TextView with id text123 has to be declared inside the Layout you set with setContentView
回答3:
Your problem is you are trying to do .show() on a AlertDialog Builder, not the AlertDialog itself.
Try the following code:
public class Xyz extends Activity {
public void onCreate(...) { // some listener will trigger initSearch() }
private void initSearch() {
AlertDialog.Builder searchDialog = new AlertDialog.Builder(this);
LayoutInflater inflater = this.getLayoutInflater();
searchDialog.setTitle("Search Photos");
searchDialog.setMessage("Specify tag and value...");
// R.layout.search_dialog is my custom layour, it displays fine, it works.
searchDialog.setView(inflater.inflate(R.layout.search_dialog, null));
EditText tagText = (EdiText) findViewById(R.id.tagField); // WILL RETURN NULL
searchDialog.setPositiveButton( ... ) ...
AlertDialog myAlert = searchDialog.create(); //returns an AlertDialog from a Builder.
myAlert.show();
}
回答4:
I had the exact same problem while programming a multilingual app. Eventually I found out that I forgot to update labels in some layout's activity [xml] files.
I had 3 of them per activity:
<activity_name>.xml
<activity_name>.xml(land)
<activity_name>.xml(iw)
I updated only the first and forgot to update the other as follows:
All three had the a single TextView with the id of:
<TextView
android:id="@+id/loading_textbox"
.../>
Then I've changed the name of the id of that text view - only in the first file - to:
<TextView
android:id="@+id/status_textbox"
.../>
And, of-course, in the Activity's Java code (that uses all three...):
TextView tv = findViewByID(R.id.status_textbox);
This worked for the regular (English <activity_name>.xml) version.
But when I went the the IW language (Hebrew <activity_name>xml(iw)) tv got null value and I even got some crushes.
When I changed the text view id of the other files to "@+id/status_textbox" everything worked like a charm...
So, simply make sure all your IDs are updated and accounted for in all your layouts and languages.
This solved my problem anyway..
来源：https://stackoverflow.com/questions/16192378/findviewbyid-returns-null-for-views-in-a-dialog