问题：我的FragmentHome上有一个ImageButton，我试图实现该按钮来打开AddEntry Fragment，以便用户可以向数据库添加信息。每次我点击ImageButton时都会崩溃：/
我还在学习Android Studio / Java，这是我第一次使用应用程序。
再次感谢您
logcat的：
04-06 01:10:12.873 5449-5449/com.example.treycoco.calorietracker E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.treycoco.calorietracker, PID: 5449
java.lang.IllegalStateException: Could not find method Click(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatImageButton with id 'AddItems'
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:325)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:284)
at android.view.View.performClick(View.java:5697)
at android.view.View$PerformClick.run(View.java:22526)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
更新LogCat：
04-06 01:32:18.745 30188-30188/com.example.treycoco.calorietracker E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.treycoco.calorietracker, PID: 30188
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getId()' on a null object reference
at com.example.treycoco.calorietracker.FragmentHome$1.onClick(FragmentHome.java:61)
at android.view.View.performClick(View.java:5697)
at android.view.View$PerformClick.run(View.java:22526)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
fragment_home.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:fab="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorBackground"
tools:context="layout.HomeFragment"
android:id="@+id/HomeFragment">
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:weightSum="1"
android:id="@+id/linearLayout">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Welcome,"
android:id="@+id/textView"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true" />
<TextView
android:layout_width="138dp"
android:layout_height="36dp"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="@string/emptyString"
android:id="@+id/User"
android:layout_gravity="center_horizontal|top"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<TextView android:id="@+id/section_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="left"
android:layout_below="@+id/linearLayout2"
android:layout_centerHorizontal="true" />
</LinearLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="355dp"
android:layout_gravity="center|bottom">
<ListView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:id="@+id/listView"
android:layout_gravity="center_horizontal"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true" />
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/AddItems"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:src="@drawable/add"
android:background="@color/colorBackground"
android:onClick="Click"
android:clickable="true" />
</RelativeLayout>
</FrameLayout>
FragmentHome.java
public class FragmentHome extends Fragment implements
View.OnClickListener {
public static final String ARG_SECTION_NUMBER = "section_number";
public static final String ARG_ID = "_id";
private TextView label;
private int sectionNumber = 0;
private Calendar fragmentDate;
ListView listview;
ImageButton AddEntrybtn;
CalorieDatabase calorieDB;
private View v;
private android.support.v4.app.FragmentManager fragmentManager;
private FragmentTransaction fragmentTransaction;
public FragmentHome() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.fragment_home, container,
false);
label= (TextView) myView.findViewById(R.id.section_label);
return myView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Bundle username = getActivity().getIntent().getExtras();
String username1 = username.getString("Username");
TextView userMain= (TextView) getView().findViewById(R.id.User);
userMain.setText(username1);
AddEntrybtn = (ImageButton)getView().findViewById(R.id.AddItems);
openDataBase();
}
private void openDataBase (){
calorieDB= new CalorieDatabase(getActivity());
calorieDB.open();
}
private void closeDataBase(){
calorieDB.close();
};
private void populateLVFromDB(){
Cursor cursor = calorieDB.getAllRows();
String[] fromFieldNames = new String[]
{CalorieDatabase.KEY_NAME, CalorieDatabase.KEY_CalorieValue};
int[] toViewIDs = new int[]
{R.id.foodEditText, R.id.caloriesEditText, };
SimpleCursorAdapter myCursorAdapter =
new SimpleCursorAdapter(
getActivity(),
R.layout.row_item,
cursor,
fromFieldNames,
toViewIDs
);
listview = (ListView) getActivity().findViewById(R.id.listView);
listview.setAdapter(myCursorAdapter);
}
@Override
public void onResume() {
super.onResume();
// set label to selected date. Get date from Bundle.
int dayOffset = sectionNumber - FragmentHomeDayViewPager.pagerPageToday;
fragmentDate = Calendar.getInstance();
fragmentDate.add(Calendar.DATE, dayOffset);
SimpleDateFormat sdf = new SimpleDateFormat(appMain.dateFormat);
String labelText = sdf.format(fragmentDate.getTime());
switch (dayOffset) {
case 0:
labelText += " (Today)";
break;
case 1:
labelText += " (Tomorrow)";
break;
case -1:
labelText += " (Yesterday)";
break;
}
label.setText(labelText);
}
@Override
public void onDestroy() {
super.onDestroy();
}
@Override
public void onDetach() {
super.onDetach();
startActivity( new Intent(getContext(),MainActivity.class));
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.AddItems:
AddEntry addEntry = new AddEntry();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder,addEntry)
.commit();
break;
}
}
}
appMain.java
public class appMain extends AppCompatActivity implements
AdapterView.OnItemClickListener {
private ActionBarDrawerToggle actionBarDrawerToggle;
public static String dateFormat = "E MMM d yyyy";
private DrawerLayout drawerLayout;
private ListView drawerList;
private android.support.v4.app.FragmentManager fragmentManager;
private FragmentTransaction fragmentTransaction;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.app_main);
drawerLayout=(DrawerLayout)findViewById(R.id.drawerlayout);
drawerList= (ListView) findViewById(R.id.drawerList);
ArrayList<String> ListArray= new ArrayList<String>();
ListArray.add("home");
ListArray.add("Add Calories");
ListArray.add("Bmi Tracker");
ListArray.add("About App");
ListArray.add("Settings");
ListArray.add("Logout");
drawerList.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
ArrayAdapter<String> adapter= new ArrayAdapter<String>(this,android.R.layout.simple_list_item_activated_1,ListArray);
drawerList.setAdapter(adapter);
drawerList.setOnItemClickListener(this);
actionBarDrawerToggle=new ActionBarDrawerToggle(this,drawerLayout,R.string.navigation_drawer_open,
R.string.navigation_drawer_close);
drawerLayout.setDrawerListener(actionBarDrawerToggle);
ActionBar actionBar= getSupportActionBar();
actionBar.setDisplayShowHomeEnabled(true);
actionBar.setDisplayHomeAsUpEnabled(true);
String username = getIntent().getStringExtra("Username");
TextView userMain = (TextView) findViewById(R.id.User);
userMain.setText(username);
fragmentManager=getSupportFragmentManager();
fragmentTransaction = fragmentManager.beginTransaction();
loadSelection(0);
}
private void loadSelection(int i){
drawerList.setItemChecked(i,true);
switch (i) {
case 0:
FragmentHome homeFragment = new FragmentHome();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder, homeFragment)
.commit();
break;
case 1:
AddEntry addEntry = new AddEntry();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder,addEntry)
.commit();
break;
case 2:
BmiFrag myBiFragment = new BmiFrag();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder, myBiFragment)
.commit();
break;
case 3:
AboutApp aboutApp = new AboutApp();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder, aboutApp)
.commit();
break;
case 4 :
break;
}
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
actionBarDrawerToggle.syncState();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id=item.getItemId();
if ( id==R.id.action_settings){
return true;
}
else if (id==android.R.id.home){
if(drawerLayout.isDrawerOpen(drawerList)){
drawerLayout.closeDrawer(drawerList);
}
else {
drawerLayout.openDrawer(drawerList);
}
}
return super.onOptionsItemSelected(item);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
switch (position){
case 0:
loadSelection(position);
break;
case 1:
loadSelection(position);
break;
case 2:
loadSelection(position);
break;
case 3:
loadSelection(position);
break;
case 4:
loadSelection(position);
break;
case 5:
Intent i = new Intent(this, MainActivity.class);
startActivity(i);
break;
}
drawerLayout.closeDrawer(drawerList);
}
public void setTitle(String title) {
getSupportActionBar().setTitle(title);
}
public void ButtonClick (View v) {
switch (v.getId()) {
case R.id.BtnBMi:
break;
}
}
}
答案 0 :(得分：0)
首先删除 android:onClick="Click"
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/AddItems"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:src="@drawable/add"
android:background="@color/colorBackground"
/>
然后
ImageButton btn = (ImageButton) myView.findViewById(R.id.AddItems);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// Add your Staff
}
});
在View onCreateView部分添加此内容。
答案 1 :(得分：0)
取出onClick
中的代码 case R.id.AddItems:
AddEntry addEntry = new AddEntry();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder,addEntry)
.commit();
break;
}
并将其放入方法Click。
例如：
private void Click{
AddEntry addEntry = new AddEntry();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder,addEntry)
.commit();
}
答案 2 :(得分：0)
首先：删除xml中的行 android：onClick =“点击”
二：删除onActivityCreated中的行
AddEntrybtn = (ImageButton) getView().findViewById(R.id.AddItems);
三：在onCreateView中调用它
AddEntrybtn = (ImageButton) myView.findViewById(R.id.AddItems);
AddEntrybtn.setOnClickListener(this);
答案 3 :(得分：0)
：
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/AddItems"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:src="@drawable/add"
android:background="@color/colorBackground"
/>
在HomeFragment.java中
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.fragment_home, container,
false);
label= (TextView) myView.findViewById(R.id.section_label);
ImageButton btn = (ImageButton) myView.findViewById(R.id.AddItems);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
//Call the Activity method where you add fragments
((appMain)getActivity()).loadSelection(4);
}
});
return myView;
}
添加方法appMain.java
public void loadSelection(int i){
drawerList.setItemChecked(i,true);
switch (i) {
case 0:
FragmentHome homeFragment = new FragmentHome();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder, homeFragment)
.commit();
break;
case 1:
AddEntry addEntry = new AddEntry();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder,addEntry)
.commit();
break;
case 2:
BmiFrag myBiFragment = new BmiFrag();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder, myBiFragment)
.commit();
break;
case 3:
AboutApp aboutApp = new AboutApp();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder, aboutApp)
.commit();
break;
case 4 :
AddEntry addEntry = new AddEntry();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.FragmentHolder,addEntry)
.commit();
break;
}
}