如何在微调器上将TextView的文本设置为所选项目的内容？

Question

I'm trying to get the value of the selected item into a TextView, and i want it to change each time the selected item change! I've try to get the position of the selected item into a string then set the text of the TextView equal to this same string but no sucess ! I'm really really new on java coding, all answer is really welcome !

Main Activity:

 package com.barcala.android.smiteultimatecountdown; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.MenuItem; import android.view.View; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.Spinner; import android.widget.TextView; import android.widget.Toast; import org.w3c.dom.Text; import static android.icu.lang.UCharacter.GraphemeClusterBreak.T; import static com.barcala.android.smiteultimatecountdown.R.array.godsNames; import static com.barcala.android.smiteultimatecountdown.R.id.god_List; import static com.barcala.android.smiteultimatecountdown.R.id.selected_God; import static com.barcala.android.smiteultimatecountdown.R.string.selected_god; public class ultimate extends AppCompatActivity { Spinner gl; String god1; TextView selectedGod; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_ultimate); selectedGod = (TextView) findViewById(R.id.selected_God); selectedGod.setText(selected_god); addListenerOnSpinnerItemSelection(); } public void addListenerOnSpinnerItemSelection() { gl = (Spinner) findViewById(R.id.god_List); gl.setOnItemSelectedListener(new MyOnItemSelectedListener()); } public void get_name(View view) { Spinner god_List = (Spinner) findViewById(R.id.god_List); god1 = god_List.getSelectedItem().toString(); TextView selectedGod = (TextView) findViewById(R.id.selected_God); selectedGod.setText(god1); } } 

MyOnItemSelectedListener() :

 package com.barcala.android.smiteultimatecountdown; import android.view.View; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.Spinner; import android.widget.Toast; import android.widget.TextView; import org.w3c.dom.Text; import static android.R.attr.y; import static com.barcala.android.smiteultimatecountdown.R.id.god_List; import static com.barcala.android.smiteultimatecountdown.R.id.selected_God; import static com.barcala.android.smiteultimatecountdown.R.string.selected_god; public class MyOnItemSelectedListener extends ultimate implements AdapterView.OnItemSelectedListener { @Override public void onItemSelected(AdapterView parent, View view, int pos, long id) { String result = parent.getItemAtPosition(pos).toString(); selectedGod.setText(result); Toast.makeText(parent.getContext(), "Selected God : " + result , Toast.LENGTH_SHORT).show(); } @Override public void onNothingSelected(AdapterView parent) { } } 

The logcat:

 03-05 15:12:09.966 19007-19007/com.barcala.android.smiteultimatecountdown E/AndroidRuntime: FATAL EXCEPTION: main Process: com.barcala.android.smiteultimatecountdown, PID: 19007 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference at com.barcala.android.smiteultimatecountdown.MyOnItemSelectedListener.onItemSelected(MyOnItemSelectedListener.java:26) at android.widget.AdapterView.fireOnSelected(AdapterView.java:1124) at android.widget.AdapterView.access$200(AdapterView.java:54) at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:1089) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:145) at android.app.ActivityThread.main(ActivityThread.java:5951) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195) 

Answer 1

Above your line for the Toast, put this line:

g1.setText(mAdapter.getItem(adapterView.getSelectedItemPosition()));

But for it to work you need to make your adaptor accessible. So set the adapter up next to the "TextView g1" and put them at the top of the Activity rather than inside the listener:

TextView g1;
ArrayAdapter<CharSequence> mAdapter;

Edit in response to comment:

Put the g1 and mAdapter at the top of the Activity:

public class MainActivity {

    TextView mG1;
    ArrayAdapter<CharSequence> mAdapter;
    ...
}

Answer 2

string.xml

<string-array name="array_name">
<item>Array Item One</item>
<item>Array Item Two</item>
<item>Array Item Three</item>
</string-array>

layout

<Spinner 
        android:id="@+id/spinner"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:drawSelectorOnTop="true"
        android:entries="@array/array_name"
    />

Activity class

String[] myarray;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    myarray = getResources().getStringArray(R.array.array_name);
}

your class

public class MyOnItemSelectedListener  implements AdapterView.OnItemSelectedListener {

    TextView g1;


        @Override
        public void onItemSelected(AdapterView parent, View view, int pos, long id) {



                 String result = myarray[pos]; 
                Toast.makeText(parent.getContext(), "Selected Country : " + result , Toast.LENGTH_SHORT).show();
                g1.setText(result);

        }

        @Override
        public void onNothingSelected(AdapterView parent) {

        }
    }