我是Android新手。我正在使用exicting sqlite db开发SQLite简单应用程序。 Launcher Activity使用listview显示来自SQLite db的数据列表。当用户在Launcher Activity中单击一个Item时，它将转到Next Activity（Details Activity）。在Next Activity中，我想让用户从应用程序的输入中更新数据库。对于更新数据库，我添加了onoptionsitem菜单按钮（编辑信息）。当用户单击onOptionsitem项目按钮时，它将转到另一个活动。在另一个活动中，将有三个（编辑文本）接受来自用户的输入。和“保存”按钮将新数据保存到现有数据库。
问题：我正面临onOptionsMenu项Null指针异常的问题，也没有保存到数据库。
任何人都可以帮助我吗？ 欢迎所有的建议和意见
这是我的代码
下一个Activity.java
public class CompDetail extends Activity {
//ArrayList<GS> q = new ArrayList<GS>();
private GS gs;
CustomAdapter adapter;
private TextView tv_title, tv_address, tv_phno;
String name, address, phone, lat, lng;
Bundle extra;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
// ////////// Action Bar ///////
ActionBar actionBar = getActionBar();
// DBAdapter
DBAdapter db = DBAdapter.getDBAdapter(getApplicationContext());
if (!db.checkDatabase()) {
db.createDatabase(getApplicationContext());
}
db.openDatabase();
extra = getIntent().getExtras();
String id = extra.getString("id");
findId();
Cursor c = db.getDetailInfoById(id, 0);
int count = c.getCount();
if (count > 0) {
while (c.moveToNext()) {
name = c.getString(c.getColumnIndex("name"));
phone = c.getString(c.getColumnIndex("phone"));
address = c.getString(c.getColumnIndex("addr"));
tv_title.setText(name);
tv_address.setText(address);
tv_phno.setText(phone);
}
}
private void findId() {
// TODO Auto-generated method stub
tv_title = (TextView) findViewById(R.id.tv_title);
tv_address = (TextView) findViewById(R.id.tv_address);
tv_phno = (TextView) findViewById(R.id.tv_phno);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.second_action_bar, menu);
return super.onCreateOptionsMenu(menu);
}
//Error
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.editinfo:
Intent i = new Intent(getApplicationContext(), EditInfo.class);
i.putExtra("idforedit", gs.getId());
startActivity(i);
return true;
case R.id.editpin:
Intent intent=new Intent(getApplicationContext(),EditMap.class);
startActivity(intent);
return true;
default:
break;
}
return super.onOptionsItemSelected(item);
}
class CustomAdapter extends ArrayAdapter<GS> {
ArrayList<GS> list;
LayoutInflater mInfalter;
private String param;
public CustomAdapter(Context context, ArrayList<GS> list) {
super(context, R.layout.detail_text, list);
this.list = list;
mInfalter = LayoutInflater.from(context);
for (int i = 0; i < list.size(); i++) {
Log.i("................", "" + list.get(i).getId());
}
}
@Override
public View getView(final int position, View convertView,
ViewGroup parent) {
ViewHolder holder;
Log.i("..........", "Hello in getView");
convertView = mInfalter.inflate(R.layout.activity_detail, parent,
false);// --customlayout.xml
// must
// have
// a
// textView
holder = new ViewHolder();
holder.name = (TextView) convertView.findViewById(R.id.tv_title);
// holder.address = (TextView)
// convertView.findViewById(R.id.textView1);
// holder.phno = (TextView)
// convertView.findViewById(R.id.textView1);
// convertView.setTag(holder);
// final int i = convertView.getId();
// } else {
// holder = (ViewHolder) convertView.getTag();
// }
holder.name.setText(list.get(position).getName());
convertView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// Toast.makeText(
// getBaseContext(),
// "Position data" + position
// + q.get(position).getId(),
// Toast.LENGTH_SHORT).show();
Intent i = new Intent(getApplicationContext(),
EditInfo.class);
i.putExtra("id", gs.getId());
startActivity(i);
}
});
return convertView;
}
}
static class ViewHolder {
TextView name;
TextView address;
TextView phno;
}
}
EditInfo.java
public class EditInfo extends Activity {
//ArrayList<GS> q = new ArrayList<GS>();
GS gs = new GS();
private String id = "";
private String city = "";
Bundle extra;
String name, address1,address2, phone;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_info);
extra = getIntent().getExtras();
String id = extra.getString("idforedit");
DBAdapter db = DBAdapter.getDBAdapter(getApplicationContext());
if (!db.checkDatabase()) {
db.createDatabase(getApplicationContext());
}
db.openDatabase();
extra = getIntent().getExtras();
String id1 = extra.getString("idforedit");
Cursor c = db.getDetailInfoById(id1, 1);
int count = c.getCount();
if (count > 1) {
while (c.moveToNext()) {
final EditText txtEditname = (EditText) findViewById(R.id.btn_name);
txtEditname.setText(name);
final EditText txtStr = (EditText) findViewById(R.id.btn_addr1);
txtStr.setText(address1);
final EditText txtAddr = (EditText) findViewById(R.id.btn_addr2);
txtAddr.setText(address2);
final EditText txtPh1 = (EditText) findViewById(R.id.btn_phno);
txtPh1.setText(phone);
Button btnsave=(Button) findViewById(R.id.btn_save);
btnsave.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
DBAdapter db = DBAdapter.getDBAdapter(getApplicationContext());
String name = txtEditname.getText().toString();
String address = txtStr.getText().toString() + ","
+ txtAddr.getText().toString();
gs.setName(name);
gs.setAddress(address);
gs.setPhno(txtPh1.getText().toString());
if ((db).EditInfo(gs)) {
Toast.makeText(getBaseContext(), "Update Successful",
Toast.LENGTH_SHORT).show();
finish();
} else {
Toast.makeText(getBaseContext(), "Update Fail",
Toast.LENGTH_SHORT).show();
}
}
});
Button btnCancel = (Button) findViewById(R.id.btn_cancel);
btnCancel.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
}
}
Database_Adapter.java
public class DBAdapter extends SQLiteOpenHelper {
CustomAdapter adapter;
static String name = "mydb.db";
static String path = "";
static ArrayList<GS> gs;
static SQLiteDatabase sdb;
DBAdapter(Context v) {
super(v, name, null, 1);
path = "/data/data/" + v.getApplicationContext().getPackageName()
+ "/databases";
}
public boolean checkDatabase() {
SQLiteDatabase db = null;
try {
db = SQLiteDatabase.openDatabase(path + "/" + name, null,
SQLiteDatabase.OPEN_READONLY);
} catch (Exception e) {
e.printStackTrace();
}
if (db == null) {
return false;
} else {
db.close();
return true;
}
}
public static synchronized DBAdapter getDBAdapter(Context v) {
return (new DBAdapter(v));
}
public void createDatabase(Context v) {
this.getReadableDatabase();
try {
InputStream myInput = v.getAssets().open(name);
// Path to the just created empty db
String outFileName = path + "/" + name;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
} catch (IOException e) {
System.out.println(e);
}
}
public void openDatabase() {
try {
sdb = SQLiteDatabase.openDatabase(path + "/" + name, null,
SQLiteDatabase.OPEN_READWRITE);
} catch (Exception e) {
System.out.println(e);
}
}
Cursor getDetailInfoById(String id, int i) {
// TODO Auto-generated method stub
Cursor Cur = null;
SQLiteDatabase db = this.getReadableDatabase();
try {
GS q1 = new GS();
Cur = db.rawQuery("select * from customer where customer_uid = '"
+ id + "'", null);
q1.setName(Cur.getString(3));
q1.setAddress(Cur.getString(7) + " " + Cur.getString(8) + " "
+ Cur.getString(5));
q1.setPhno(Cur.getString(16));
String latlng = Cur.getString(38);
String[] arr = latlng.split(",");
q1.setLat(Double.parseDouble(arr[0]));
q1.setLng(Double.parseDouble(arr[1]));
} catch (Exception e) {
// TODO: handle exception
}
int c = Cur.getCount();
return Cur;
}
}
以下是日志猫
07-06 23:14:38.934: E/AndroidRuntime(18851): FATAL EXCEPTION: main 07-06 23:14:38.934: E/AndroidRuntime(18851): java.lang.NullPointerException 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.example.location_application_v1.CompDetail.onOptionsItemSelected(CompDetail.java:203) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.app.Activity.onMenuItemSelected(Activity.java:2593) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1011) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.view.menu.MenuPopupHelper.onItemClick(MenuPopupHelper.java:259) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.widget.AdapterView.performItemClick(AdapterView.java:301) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.widget.AbsListView.performItemClick(AbsListView.java:1139) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2856) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.widget.AbsListView$1.run(AbsListView.java:3619) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.os.Handler.handleCallback(Handler.java:800) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.os.Handler.dispatchMessage(Handler.java:100) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.os.Looper.loop(Looper.java:194) 07-06 23:14:38.934: E/AndroidRuntime(18851): at android.app.ActivityThread.main(ActivityThread.java:5433) 07-06 23:14:38.934: E/AndroidRuntime(18851): at java.lang.reflect.Method.invokeNative(Native Method) 07-06 23:14:38.934: E/AndroidRuntime(18851): at java.lang.reflect.Method.invoke(Method.java:525) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:922) 07-06 23:14:38.934: E/AndroidRuntime(18851): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:689) 07-06 23:14:38.934: E/AndroidRuntime(18851): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
我猜这个错误在这行i.putExtra("idforedit", gs.getId());中，因为你没有在CompDetail类的任何地方初始化对象gs。
另外请尝试使用有意义的名字，因为我不知道gs应该是什么。