我想调用this方法(该方法放在mainActivity中):
public void setTextView(String[] countryArray, String column){
TextView myAwesomeTextView;
String textViewID;
for(int i=0; i<=25; i++) {
if(column.equals("left")){
textViewID = "textViewColumn1_" + i;
} else {
textViewID = "textViewColumn2_" + i;
}
int resID = getResources().getIdentifier(textViewID, "id", getPackageName());
myAwesomeTextView = (TextView) findViewById(resID);
myAwesomeTextView.setText(countryArray[i]);
}
}
如果我在MainActivity中调用该方法,则没有问题。 但是当用户更改应用程序的设置时,我想在我的AppCompatPreferenceActivity中调用它。但随后应用程序崩溃了:
@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
// handle the preference change here
mainActivity.setTextView(usa, "left");
}
Android监视器:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.larsus.test.testproject, PID: 56871
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
at android.content.ContextWrapper.getResources(ContextWrapper.java:85)
at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:74)
at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:548)
at com.larsus.test.testproject.ScrollingActivity.setTextView(ScrollingActivity.java:126)
at com.larsus.test.testproject.AppCompatPreferenceActivity.onSharedPreferenceChanged(AppCompatPreferenceActivity.java:50)
at android.app.SharedPreferencesImpl$EditorImpl.notifyListeners(SharedPreferencesImpl.java:476)
at android.app.SharedPreferencesImpl$EditorImpl.apply(SharedPreferencesImpl.java:384)
at android.preference.Preference.tryCommit(Preference.java:1433)
at android.preference.Preference.persistString(Preference.java:1466)
at android.preference.ListPreference.setValue(ListPreference.java:147)
at android.preference.ListPreference.onDialogClosed(ListPreference.java:282)
at android.preference.DialogPreference.onDismiss(DialogPreference.java:391)
at android.app.Dialog$ListenersHandler.handleMessage(Dialog.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5349)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:908)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:703)
问题是为什么?
答案 0 :(得分:0)
尝试这样打电话:
((MainActivity)getActivity()).setTextView(usa, "left");
我希望它有效。
答案 1 :(得分:0)
使用此方法创建一个公共类。在这个类构造函数中添加 Activity对象并使用此类对象来使用此方法。
public class TextViewText {
Activity mActivity;
public TextViewText (Activity mActivity) {
this.mActivity = mActivity;
}
public void setTextView(String[] countryArray, String column){
TextView myAwesomeTextView;
String textViewID;
for(int i=0; i<=25; i++) {
if(column.equals("left")){
textViewID = "textViewColumn1_" + i;
} else {
textViewID = "textViewColumn2_" + i;
}
int resID = getResources().getIdentifier(textViewID, "id", getPackageName());
myAwesomeTextView = (TextView) findViewById(resID);
myAwesomeTextView.setText(countryArray[i]);
}
}
}
如果要设置文字:
TextViewText tvt = new TextViewText(MainActivity.this); //your activity context
tvt.setTextView(usa, "left");