将数据从DialogFragment传递回活动
将数据从DialogFragment传递回活动
提问于 2014-01-29 19:35:56
我在对话框中设置了一个搜索字段，然后当用户单击开始打开时，允许他们输入一个标题并点击search。我希望它能够与活动的列表视图进行交流。
不幸的是，当我试图搜索的时候，我一直被撞毁。我已经使用侦听器设置了它，但是我相信它与尝试从MainActivity的布局中读取textView有关，即使它在DialogFragment中？
我试图通过R.id.searchField在MainActivity中调用它，其中onCreate的setContent的布局XML不同于DialogFragment实现的布局XML。当我试图这样做的时候没有错误，只有致命的崩溃。不知道为什么我会收到一个错误，下面是代码和堆栈跟踪：
MainActivity：
public class MainActivity extends Activity implements searchListener{
public void searchBooks()
{
// Error is in this function, believe it has to do with this textField as it resides in // the DialogFragment's xml? Unless findViewById calls from all XMLS and just not one defined in
//setContentView for the activity? Not sure though, initially I feel I should have this searchField
//defined in the fragment class, but then I won't have access to it in this function in MainActivity,
//or the mResults which is where the data is being used
EditText searchField = (EditText) findViewById(R.id.searchField);
if (mResults != null && !searchField.getText().equals(""))
{
String inputedText = searchField.getText().toString();
JSONArray results = new JSONArray();
for (int i = 0; i < mResults.length(); i++)
{
try {
JSONObject bookObject = mResults.getJSONObject(i);
if (bookObject.get("name").toString().equalsIgnoreCase(inputedText))
{
results.put(bookObject);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
public void showDialog() {
DialogFrag newFragment = DialogFrag.newInstance();
newFragment.show(getFragmentManager(), "dialog");
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Setting the main view
setContentView(R.layout.activity_main_fragment);
}
}DialogFragment：
public class DialogFrag extends DialogFragment {
public static DialogFrag newInstance() {
return new DialogFrag();
}
private searchListener listener;
public interface searchListener
{
public void searchBooks();
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
listener = (searchListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + "attaching d fragment failed!");
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.search_dialog_fragment, container, false);
searchButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
listener.searchBooks();
}
});
return v;
}
}StackTrace
01-29 20:10:21.570: E/AndroidRuntime(11260): FATAL EXCEPTION: main
01-29 20:10:21.570: E/AndroidRuntime(11260): Process: com.brentadams.bookList, PID: 11260
01-29 20:10:21.570: E/AndroidRuntime(11260): java.lang.NullPointerException
01-29 20:10:21.570: E/AndroidRuntime(11260): at com.brentadams.bookList.MainActivity.searchBooks(MainActivity.java:327)
01-29 20:10:21.570: E/AndroidRuntime(11260): at com.brentadams.bookList.fragments.SearchFragment$1.onClick(SearchFragment.java:48)
01-29 20:10:21.570: E/AndroidRuntime(11260): at android.view.View.performClick(View.java:4438)
01-29 20:10:21.570: E/AndroidRuntime(11260): at android.view.View$PerformClick.run(View.java:18422)
01-29 20:10:21.570: E/AndroidRuntime(11260): at android.os.Handler.handleCallback(Handler.java:733)
01-29 20:10:21.570: E/AndroidRuntime(11260): at android.os.Handler.dispatchMessage(Handler.java:95)
01-29 20:10:21.570: E/AndroidRuntime(11260): at android.os.Looper.loop(Looper.java:136)
01-29 20:10:21.570: E/AndroidRuntime(11260): at android.app.ActivityThread.main(ActivityThread.java:5017)
01-29 20:10:21.570: E/AndroidRuntime(11260): at java.lang.reflect.Method.invokeNative(Native Method)
01-29 20:10:21.570: E/AndroidRuntime(11260): at java.lang.reflect.Method.invoke(Method.java:515)
01-29 20:10:21.570: E/AndroidRuntime(11260): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
01-29 20:10:21.570: E/AndroidRuntime(11260): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
01-29 20:10:21.570: E/AndroidRuntime(11260): at dalvik.system.NativeStart.main(Native Method)编辑新代码/错误：
接受了您的建议，将字符串传递回方法searchBooks，但是现在收到了一个愚蠢的空空异常，我认为这是没有任何意义的。textview驻留在我的activity_main_fragment.xml中：
public class MainActivity extends Activity implements searchListener{
public void searchBooks(String searchString)
{
if (mResults != null && searchString != null && !searchString.equals(""))
{
JSONArray results = new JSONArray();
for (int i = 0; i < mResults.length(); i++)
{
try {
JSONObject bookObject = mResults.getJSONObject(i);
if (bookObject.get("name").toString().equalsIgnoreCase(searchString))
{
results.put(bookObject);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
public void showDialog() {
DialogFrag newFragment = DialogFrag.newInstance();
newFragment.show(getFragmentManager(), "dialog");
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Setting the main view
setContentView(R.layout.activity_main_fragment);
}
}DialogFragment
public class DialogFrag extends DialogFragment {
public static DialogFrag newInstance() {
return new DialogFrag();
}
private searchListener listener;
public interface searchListener
{
public void searchBooks(String text);
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
listener = (searchListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + "attaching d fragment failed!");
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.search_dialog_fragment, container, false);
searchButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
EditText searchField = (EditText) v.findViewById(R.id.searchField);
String input = searchField.getText().toString();
listener.searchBooks(input);
}
});
return v;
}
}斯塔克迹
01-29 15:30:31.402: E/AndroidRuntime(777): FATAL EXCEPTION: main
01-29 15:30:31.402: E/AndroidRuntime(777): java.lang.NullPointerException
01-29 15:30:31.402: E/AndroidRuntime(777): at com.brentadams.bookList.fragments.SearchFragment$1.onClick(SearchFragment.java:51)
01-29 15:30:31.402: E/AndroidRuntime(777): at android.view.View.performClick(View.java:4084)
01-29 15:30:31.402: E/AndroidRuntime(777): at android.view.View$PerformClick.run(View.java:16966)
01-29 15:30:31.402: E/AndroidRuntime(777): at android.os.Handler.handleCallback(Handler.java:615)
01-29 15:30:31.402: E/AndroidRuntime(777): at android.os.Handler.dispatchMessage(Handler.java:92)
01-29 15:30:31.402: E/AndroidRuntime(777): at android.os.Looper.loop(Looper.java:137)
01-29 15:30:31.402: E/AndroidRuntime(777): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-29 15:30:31.402: E/AndroidRuntime(777): at java.lang.reflect.Method.invokeNative(Native Method)
01-29 15:30:31.402: E/AndroidRuntime(777): at java.lang.reflect.Method.invoke(Method.java:511)
01-29 15:30:31.402: E/AndroidRuntime(777): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-29 15:30:31.402: E/AndroidRuntime(777): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-29 15:30:31.402: E/AndroidRuntime(777): at dalvik.system.NativeStart.main(Native Method)第51行：
String input = searchField.getText().toString();回答 2
Stack Overflow用户
回答已采纳
发布于 2014-01-29 19:49:35
所以是的，问题是R.id.searchfield。它不是MainActivity的根视图的子视图，它是对话框片段的子视图。
之所以会出现空指针，是因为它找不到R.id.searchfield，结果搜索字段是空的，在调用searchField.getText()时，这会使您在下一行崩溃。
只需让您的对话框框架搜索文本字段，并将一个字符串传回给您的主要活动。
Stack Overflow用户
发布于 2014-01-29 19:47:55
findViewById()只会在您在setContentView()中指定的布局文件中找到视图。您需要将TextView移动到Activity's布局中，或者将此逻辑移动到Fragment中。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/21440856
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