Question

不确定导致错误的原因。输出说它是因为我的Fragment包含数据库逻辑。显然，错误是由addScoutData();和sqLiteDatabase = databaseHelper.getWritableDatabase();

引起的

这是片段类

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

/**
 * A simple {@link Fragment} subclass.
 */
public class AddScoutDataFragment extends Fragment {

    Button cancelButton;
    Button addDataButton;
    DatabaseHelper myDB;
    EditText tNumber, tPoticullis, tChevalFrise, tMoat, tRamparts, tDrawbridge, tSallyPort, tRockWall, tRockTerrain, tLowBar;
    Context context = this.getActivity();
    DatabaseHelper databaseHelper;
    SQLiteDatabase sqLiteDatabase;

    public AddScoutDataFragment() {
        // Required empty public constructor
    } //End of AddScoutDataFragment

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_add_scout_data, container, false);
        view.setBackgroundColor(Color.WHITE);

        //Create database
        myDB = new DatabaseHelper(getActivity());

        //Instantiate all editText objects
        tNumber = (EditText) view.findViewById(R.id.editNumber);
        tPoticullis = (EditText) view.findViewById(R.id.editPoticullis);
        tChevalFrise = (EditText) view.findViewById(R.id.editChevalFrise);
        tMoat = (EditText) view.findViewById(R.id.editMoat);
        tRamparts = (EditText) view.findViewById(R.id.editRamparts);
        tDrawbridge = (EditText) view.findViewById(R.id.editDrawbridge);
        tSallyPort = (EditText) view.findViewById(R.id.editSallyPort);
        tRockWall = (EditText) view.findViewById(R.id.editRockWall);
        tRockTerrain = (EditText) view.findViewById(R.id.editRockTerrain);
        tLowBar = (EditText) view.findViewById(R.id.editLowBar);

        //Adds data to ScoutFragment
        addDataButton = (Button) view.findViewById(R.id.buttonDataAdd);
        addDataButton.setOnClickListener(new View.OnClickListener(){
            public void onClick(View v){
                //Saves data to database
                addScoutInfo();

                //Returns to ScoutFragment
                ScoutFragment fragment = new ScoutFragment();
                FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
                fragmentTransaction.setCustomAnimations(R.anim.enter_from_left, R.anim.exit_to_right, R.anim.enter_from_right, R.anim.exit_to_left);
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.commit();
            } //End of onClick
        }); //End of setOnClickListener

        //Returns to ScoutFragment without adding any data
        cancelButton = (Button) view.findViewById(R.id.buttonCancel);
        cancelButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                //Returns to ScoutFragment
                ScoutFragment fragment = new ScoutFragment();
                FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
                fragmentTransaction.setCustomAnimations(R.anim.enter_from_left, R.anim.exit_to_right, R.anim.enter_from_right, R.anim.exit_to_left);
                fragmentTransaction.replace(R.id.fragment_container, fragment);
                fragmentTransaction.commit();
            } //End of onClick
        }); //End of setOnClickListener
        // Inflates the layout for this fragment
        return view;
    } //End of onCreateView

    public void addScoutInfo(){
        //Converts all editText values into strings
        String sNumber = tNumber.getText().toString();
        String sPoticullis = tPoticullis.getText().toString();
        String sChevalFrise = tChevalFrise.getText().toString();
        String sMoat = tMoat.getText().toString();
        String sRamparts = tRamparts.getText().toString();
        String sDrawbridge = tDrawbridge.getText().toString();
        String sSallyPort = tSallyPort.getText().toString();
        String sRockWall = tRockWall.getText().toString();
        String sRockTerrain = tRockTerrain.getText().toString();
        String sLowBar = tLowBar.getText().toString();

        //Saves data
        databaseHelper = new DatabaseHelper(context);
        sqLiteDatabase = databaseHelper.getWritableDatabase();
        databaseHelper.addInformation(sNumber, sPoticullis, sChevalFrise, sMoat, sRamparts, sDrawbridge, sSallyPort, sRockWall,
                sRockTerrain, sLowBar, sqLiteDatabase);
        Toast.makeText(getContext(), "Data Saved", Toast.LENGTH_LONG).show();
        databaseHelper.close();
    } //End of addScoutInfo
} //End of class

错误记录

3-16 00:36:47.355 5827-5827/com.compscitutorials.basigarcia.ramfernoscout E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                             Process: com.compscitutorials.basigarcia.ramfernoscout, PID: 5827
                                                                                             java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
                                                                                                 at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223)
                                                                                                 at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
                                                                                                 at com.compscitutorials.basigarcia.ramfernoscout.AddScoutDataFragment.addScoutInfo(AddScoutDataFragment.java:100)
                                                                                                 at com.compscitutorials.basigarcia.ramfernoscout.AddScoutDataFragment$1.onClick(AddScoutDataFragment.java:58)
                                                                                                 at android.view.View.performClick(View.java:5198)
                                                                                                 at android.view.View$PerformClick.run(View.java:21147)
                                                                                                 at android.os.Handler.handleCallback(Handler.java:739)
                                                                                                 at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                                 at android.os.Looper.loop(Looper.java:148)
                                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

更新以下行：

databaseHelper = new DatabaseHelper(context);

到

databaseHelper = new DatabaseHelper(getActivity());

原因：您的上下文为空。

修改1：

您需要在保存数据之前打开数据库：

databaseHelper = new DatabaseHelper(context);
databaseHelper.open();            
sqLiteDatabase = databaseHelper.getWritableDatabase();

databaseHelper.addInformation(sNumber, sPoticullis, sChevalFrise, sMoat, sRamparts, sDrawbridge, sSallyPort, sRockWall,
                sRockTerrain, sLowBar, sqLiteDatabase);
Toast.makeText(getContext(), "Data Saved", Toast.LENGTH_LONG).show();
databaseHelper.close();

希望这是有道理的。

Android - 数据库在保存数据时崩溃

1 个答案: