我需要将共享功能添加到我的Android应用程序中（该应用程序用于编写注释并将其存储在SQLite数据库中）（共享按钮仅共享注释的正文）。我做到了，但是当我按下＆＃34;分享＆＃34;按钮，显示FC（强制关闭），应用程序停止。
共享功能的代码（MainActivity类中的代码）：
...
@Override
public boolean onContextItemSelected(final MenuItem item) {
switch (item.getItemId()) {
case R.id.share:
String shareBody = NotesModel.actualNote.body;
Intent shareIntent = new Intent("android.intent.action.SEND");
shareIntent.setType("text/plain");
shareIntent.putExtra("android.intent.extra.TEXT", shareBody);
startActivity(shareIntent);
return true;
...
整个MainActivity类：
package com.twitter.i_droidi.mynotesdonation;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.preference.PreferenceManager;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.CheckBox;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;
import java.util.List;
import com.oguzdev.circularfloatingactionmenu.library.FloatingActionButton;
public class MainActivity extends ActionBarActivity implements AdapterView.OnItemClickListener, View.OnClickListener {
ListView lv;
NotesDataSource nDS;
List<NotesModel> notesList;
String[] notes;
int i;
ArrayAdapter<String> adapter;
FloatingActionButton actionButton;
public static final String floatingButtonTag = "";
CheckBox checkBox;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View checkBoxView = View.inflate(this, R.layout.checkbox, null);
checkBox = (CheckBox) checkBoxView.findViewById(R.id.checkboxDialog);
checkBox.setOnClickListener(this);
loadSavedPreferences();
checkBox.setText(R.string.do_not_show_this_again);
final Context context = this;
AlertDialog.Builder mainDialog = new AlertDialog.Builder(context);
mainDialog.setTitle(R.string.thanks);
mainDialog.setMessage(R.string.main_dialog_body);
mainDialog.setIcon(R.drawable.my_notes);
mainDialog.setView(checkBoxView);
mainDialog.setPositiveButton(R.string.welcome, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// Do Not Do Anything.
}
});
AlertDialog alertDialog = mainDialog.create();
if (checkBox.isChecked() == false) {
alertDialog.show();
}
ImageView icon = new ImageView(this);
icon.setImageDrawable(getResources().getDrawable(R.drawable.ic_action_new));
actionButton = new FloatingActionButton.Builder(this)
.setContentView(icon)
.setBackgroundDrawable(R.drawable.the_selector)
.build();
actionButton.setOnClickListener(this);
actionButton.setTag(floatingButtonTag);
nDS = new NotesDataSource(this);
lv = (ListView) findViewById(R.id.lv);
nDS.open();
notesList = nDS.getAllNotes();
nDS.close();
notes = new String[notesList.size()];
for (i = 0; i < notesList.size(); i++) {
notes[i] = notesList.get(i).getTitle();
}
adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1,
android.R.id.text1, notes);
lv.setAdapter(adapter);
registerForContextMenu(lv);
lv.setOnItemClickListener(this);
}
public void loadSavedPreferences() {
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
boolean checkBoxStatus = prefs.getBoolean("Status", false);
if (checkBoxStatus) {
checkBox.setChecked(true);
} else {
checkBox.setChecked(false);
}
}
public void savePreferences(String key, boolean status) {
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = prefs.edit();
editor.putBoolean(key, status);
editor.commit();
}
@Override
public void onClick(View v) {
if (v.getTag() != null && v.getTag().equals(floatingButtonTag)) {
Intent nNote = new Intent(this, CreateNote.class);
startActivity(nNote);
}
savePreferences("Status", checkBox.isChecked());
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent nView = new Intent(this, ViewEditNote.class);
nView.putExtra("id", notesList.get(position).getId());
nView.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(nView);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_item_selected, menu);
super.onCreateContextMenu(menu, v, menuInfo);
}
@Override
public boolean onContextItemSelected(final MenuItem item) {
switch (item.getItemId()) {
case R.id.share:
String shareBody = NotesModel.body;
Intent shareIntent = new Intent("android.intent.action.SEND");
shareIntent.setType("text/plain");
shareIntent.putExtra("android.intent.extra.TEXT", shareBody);
startActivity(shareIntent);
return true;
case R.id.delete:
AlertDialog.Builder deleteDialog = new AlertDialog.Builder(this);
deleteDialog.setTitle(getString(R.string.delete_title));
deleteDialog.setMessage(R.string.delete_body);
deleteDialog.setIcon(R.drawable.my_notes);
deleteDialog.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface deleteDialog, int witch) {
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
nDS.open();
nDS.deleteNote(notesList.get(info.position).getId());
notesList = nDS.getAllNotes();
nDS.close();
notes = new String[notesList.size()];
for (i = 0; i < notesList.size(); i++) {
notes[i] = notesList.get(i).getTitle();
}
adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1,
android.R.id.text1, notes);
lv.setAdapter(adapter);
registerForContextMenu(lv);
lv.setOnItemClickListener(MainActivity.this);
Toast nDelete = Toast.makeText(MainActivity.this, R.string.deleted, Toast.LENGTH_LONG);
nDelete.show();
return;
}
});
deleteDialog.setNegativeButton(R.string.no, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface deleteDialog, int which) {
// Do Not Do Anything.
}
});
deleteDialog.show();
return true;
}
return super.onContextItemSelected(item);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.mainMenuAbout:
AlertDialog.Builder aboutDialog = new AlertDialog.Builder(this);
aboutDialog.setTitle(getString(R.string.about_title));
aboutDialog.setMessage(R.string.about_body);
aboutDialog.setIcon(R.drawable.my_notes);
aboutDialog.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface aboutDialog, int witch) {
// Do Not Do Anything.
}
});
aboutDialog.show();
return true;
case R.id.mainMenuBackupHelp:
AlertDialog.Builder backupHelpDialog = new AlertDialog.Builder(this);
backupHelpDialog.setTitle(getString(R.string.backup_help_title));
backupHelpDialog.setMessage(R.string.backup_help_body);
backupHelpDialog.setIcon(R.drawable.my_notes);
backupHelpDialog.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface backupHelpDialog, int witch) {
// Do Not Do Anything.
}
});
backupHelpDialog.show();
return true;
}
return super.onOptionsItemSelected(item);
}
}
NotesModel类：
package com.twitter.i_droidi.mynotesdonation;
public class NotesModel {
int id;
String title;
String body;
static NotesModel actualNote;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getBody() {
return body;
}
public void setBody(String body) {
this.body = body;
}
}
NotesDataSource类：
package com.twitter.i_droidi.mynotesdonation;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import java.util.ArrayList;
import java.util.List;
public class NotesDataSource {
DB myDB;
SQLiteDatabase sql;
public static NotesModel note;
String[] getAllColumns = new String[]{DB.ID, DB.TITLE, DB.BODY};
public NotesDataSource(Context context) {
myDB = new DB(context);
}
public void open() {
try {
sql = myDB.getWritableDatabase();
} catch (Exception ex) {
Log.d("Error in your database!", ex.getMessage());
}
}
public void close() {
sql.close();
}
public void createNote(String title, String body) {
ContentValues note = new ContentValues();
note.put(myDB.TITLE, title);
note.put(myDB.BODY, body);
sql.insert(myDB.TABLE_NAME, null, note);
}
public NotesModel getNote(int id) {
note = new NotesModel();
Cursor cursor = sql.rawQuery("SELECT * FROM " + DB.TABLE_NAME + " WHERE " + DB.ID + " = ?", new String[]{id + ""});
if (cursor.getCount() > 0) {
cursor.moveToFirst();
note.setId(cursor.getInt(0));
note.setTitle(cursor.getString(1));
note.setBody(cursor.getString(2));
cursor.close();
}
return note;
}
public void updateNote(int id, String title, String body) {
ContentValues note = new ContentValues();
note.put(myDB.TITLE, title);
note.put(myDB.BODY, body);
sql.update(myDB.TABLE_NAME, note, myDB.ID + " = " + id, null);
}
public void deleteNote(Object id) {
sql.delete(myDB.TABLE_NAME, myDB.ID + " = " + id, null);
}
public List<NotesModel> getAllNotes() {
List<NotesModel> notesList = new ArrayList<NotesModel>();
Cursor cursor = sql.query(myDB.TABLE_NAME, getAllColumns, null, null, null, null, null);
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
NotesModel notes = new NotesModel();
notes.setId(cursor.getInt(0));
notes.setTitle(cursor.getString(1));
notes.setBody(cursor.getString(2));
notesList.add(notes);
cursor.moveToNext();
}
cursor.close();
return notesList;
}
}
logcat：
09-06 01:53:10.263 24553-24553/com.twitter.i_droidi.mynotesdonation E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.twitter.i_droidi.mynotesdonation, PID: 24553
java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.twitter.i_droidi.mynotesdonation.NotesModel.body' on a null object reference
at com.twitter.i_droidi.mynotesdonation.MainActivity.onContextItemSelected(MainActivity.java:144)
at android.app.Activity.onMenuItemSelected(Activity.java:2905)
at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:325)
at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:147)
at android.support.v7.internal.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:100)
at com.android.internal.policy.impl.PhoneWindow$DialogMenuCallback.onMenuItemSelected(PhoneWindow.java:4701)
at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:761)
at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:904)
at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:894)
at com.android.internal.view.menu.MenuDialogHelper.onClick(MenuDialogHelper.java:167)
at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:1082)
at android.widget.AdapterView.performItemClick(AdapterView.java:305)
at android.widget.AbsListView.performItemClick(AbsListView.java:1146)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3053)
at android.widget.AbsListView$3.run(AbsListView.java:3860)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
答案 0 :(得分：1)
好像你没有初始化NotesModel类中的actualNote字段。试着说
static NotesModel actualNote = new NotesModel();
答案 1 :(得分：0)
在这种情况下，为什么要制作内部静态对象，只需使用：
public class NotesModel {
int id;
String title;
public static String body;
...
}
并获取如：
NotesModel.body
编辑：
如果您不想要static标识符，请使用Getter方法：
NotesModel mModel = new NotesModel();
mModel.setBody(" String with your body ");
String shareBody = mModel.getBody(); // Getter method