我正在尝试构建一个示例应用,该应用在同一活动中具有两个片段。一个片段具有EditText,SeekBar和一个Button。第二个片段有一个TextView。在第一个片段的EditText中输入文本,并将seekbar设置为适当的值,然后单击按钮将更改第二个片段中的文本,并在第一个片段中输入文本,大小由seekbar描述。我写了一个不错的代码,但该应用程序在单击按钮时一直崩溃。请帮助!
片段一:
import ....
public class Toolbarfragment extends Fragment implements OnSeekBarChangeListener {
private static int seekvalue = 10;
private static EditText edittext;
public interface ToolbarListener {
void onButtonClick(int pos, String tex);
}
ToolbarListener activityCallback;
@Override
public View onCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.toolbarfragment, container, false);
edittext= (EditText)view.findViewById(R.id.editTextTextPersonName);
final Button button = (Button) view.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
buttonclicked(v);
}
});
final SeekBar seekBar = (SeekBar) view.findViewById(R.id.seekBar);
seekBar.setOnSeekBarChangeListener(this);
return view;
}
public void buttonclicked(View view) {
activityCallback.onButtonClick(seekvalue, edittext.getText().toString());
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
seekvalue = progress;
}
@Override
public void onStartTrackingTouch(SeekBar arg0) {
}
@Override
public void onStopTrackingTouch(SeekBar arg0) {
}
}
片段二:
import ...
public class TextFragment extends Fragment {
private static TextView textview;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view= inflater.inflate(R.layout.textfragment,container,false);
textview = view.findViewById(R.id.textView);
return view;
}
public void changetextproperties(int size, String text) {
textview.setText(text);
textview.setTextSize(size);
}
}
主要活动:
import ...
public class MainActivity extends FragmentActivity implements Toolbarfragment.ToolbarListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public void onButtonClick(int size, String text) {
TextFragment textfragment= (TextFragment)getSupportFragmentManager().findFragmentById(R.id.fragment2);
textfragment.changetextproperties(size, text);
}
}
Logcat:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.badatext, PID: 13829
java.lang.NullPointerException: Attempt to invoke interface method 'void com.example.badatext.Toolbarfragment$ToolbarListener.onButtonClick(int, java.lang.String)' on a null object reference
at com.example.badatext.Toolbarfragment.buttonclicked(Toolbarfragment.java:52)
at com.example.badatext.Toolbarfragment$1.onClick(Toolbarfragment.java:37)
at android.view.View.performClick(View.java:6597)
at android.view.View.performClickInternal(View.java:6574)
at android.view.View.access$3100(View.java:778)
at android.view.View$PerformClick.run(View.java:25885)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6669)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
想通!
您可以使用localbrodcastreceiver,也可以在启动片段时使用来自意图的其他值