onClick：Android Studio中的EditText为空

Question

I have the most simple code and it have worked before but now for some reason it doesn't and I can't figure out why! And the problem is quite hard to google.

I am unable to get the text from the EditText . I've created a new project, I've copied the exact code from another project (where it works) but here it just won't work. I'm hoping the problem is really obvious and i've just been staring at it for too long.

    import android.app.Activity;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.widget.EditText;

    public class MainActivity extends Activity {
    String artist;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        EditText edit = (EditText) findViewById(R.id.artistEditText);
        artist = edit.getText().toString();

    }

    protected void tryLetter(View v){
        System.out.println(artist);
        Log.d("string", artist);
        System.out.println("hi");
    }
}

The println to print artist doesn't show at all and neither does the Log.d and tryletter is called when I press a button.

Here is the layout file if it makes a difference.

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="Ange en artist:"
    android:id="@+id/artistTextLabel"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="30dp" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/artistEditText"
    android:layout_alignBottom="@+id/artistTextLabel"
    android:layout_alignEnd="@+id/searchBtn" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Sök"
    android:id="@+id/searchBtn"
    android:onClick="tryLetter"
    android:layout_below="@+id/artistEditText"
    android:layout_centerHorizontal="true" />
</RelativeLayout>

Answer 1

put this artist = edit.getText().toString(); inside this tryLetter because you need to fetch the text from EditText when action is performed mean onClick and make your tryLetter method public

because it will only work when your method is public

so use this

public void tryLetter(View v){
    artist = edit.getText().toString();
    System.out.println(artist);
    Log.d("string", artist);
    System.out.println("hi");
}

instead of this protected void tryLetter(View v){

Answer 2

In simple scenarios like yours, something needs to trigger to get the data from the EditText. The best would be to place the fetch code, inside a trigger say A Button's block of code or inside a listener

Answer 3

In your example there are two mistakes:

1. Method tryLetter has protected modifier. that will not make this
   method visible to layout. and you get exception :
   IllegalStateException. solution by making it public.
2. You hold immutable value content of EditText as string inside onCreate by assigning it into artist. it's empty by default and wont be change later when you insert content to EditText. Solution will be to hold instance of
   EditText and extract String from it for each click dynamically.

Here is your code with two fixes:

import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.util.Log; import android.view.View; import android.widget.EditText;

public class MainActivity extends AppCompatActivity {
    private EditText edit;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         edit = (EditText) findViewById(R.id.artistEditText);
    }

    public void tryLetter(View v){
        String artist=edit.getText().toString();
        System.out.println(artist);
        Log.d("string", artist);
        System.out.println("hi");
    }
}