大佬教程收集整理的这篇文章主要介绍了Android Studio：SQLite 某种形式的测验。在 logcat 中出现错误，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。
我在运行我的应用程序时遇到错误。我应该从我创建的数据库中获取我的照片数据，并添加了这些值。我查看了所有可能的在线资源，当它说我正在调用的参数中没有数据时，我真的无法弄清楚为什么我得到空值。这是我第一次在这里提问，所以不要介意我不知道这些功能。也是我第一次使用 sqlite 和 androID studio。 FYP 截止日期即将到来，因此我很困:(
我的错误上线了 photoQuestion.setText(currentQuestion.getPhoto) 它说我数据库的那一列基本上没有数据
PeopleModeActivity（主要活动）
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sqliteDbHandler
public class PeopleModeActivity extends AppCompatActivity {
private PeopleMode PEOPLEMODE;
private PeopleModeQuestions currentQuestion; // current question that is accessed
private int relativeS_ID; // current relatives ID that is accessed (Question_ID)
private sqliteDbHandler DbHandler; // database handler
private ArrayList<PeopleModeAnswers> currentQuestion_Answers; // store List of answers to respective questions
private PeopleModeAnswers relationshipOption_1; // variable in reference to relationships option 1
private PeopleModeAnswers relationshipOption_2; // variable in reference to relationships option 2
private TextVIEw photoQuestion; // UI for question (display photo)
private button buttonOption1; // UI for relationships option 1
private button buttonOption2; // UI for relationships option 2
@OverrIDe
protected voID onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentVIEw(R.layout.activity_people_mode);
DbHandler = new sqliteDbHandler(this);
// Obtain the Intent which contains extra values inserted in the prevIoUs Activity
// The values to retrIEve and use: PEOPLEMODE,relativeS_ID
// If game mode with same PatIEnt ID is going on,the values (such as questions and answers for that patIEnt ID will carry forward)
Intent intent = getIntent();
// Game mode intialisation
PEOPLEMODE = intent.getParcelableExtra("PEOPLEMODE");
// current relativeS_ID initialisation
relativeS_ID = intent.getIntExtra("relativeS_ID",1);
// To make sure that the game ends and goes to congratulations screen
// when all questions of the ongoing patIEnt ID finishes
// There are 4 questions (relatives_ID) in the PEOPLE MODE,so 4 will be used as counter to kNow when to end
if (relativeS_ID > 4) {
Intent congratulations_screen = new Intent(PeopleModeActivity.this,EndOfQuestionsActivity.class);
congratulations_screen.putExtra("PEOPLEMODE",PEOPLEMODE);
startActivity(congratulations_screen);
}
// there are still more questions (relatives_ID),people mode will continue and carry forward prevIoUs question data if any
// such as current relatives_ID
else {
// current question initialisation (in reference to photo associated with current relativesID)
// current questions based on current relativesID will be
// stored in a PeopleModeQuestions object
currentQuestion = DbHandler.getrelativesPhotoQuestion(relativeS_ID);
// RetrIEve the List that stores the answers related to the current question (relatives_ID)
// List created in db will be called,getrelativesPhotoAnswersByrelativesID
currentQuestion_Answers = (ArrayList) DbHandler.getrelativesPhotoAnswersByrelativesID(relativeS_ID);
// Initialise all the relationships answers for the people mode
relationshipOption_1 = currentQuestion_Answers.get(0);
relationshipOption_1 = currentQuestion_Answers.get(1);
// display the Photo (Question) in the screen
photoQuestion = (TextVIEw) findVIEwByID(R.ID.photoQuestiontest);
photoQuestion.setText(currentQuestion.getPhoto());
// display the relationships options (Answers) in the screen
buttonOption1 = findVIEwByID(R.ID.option1);
buttonOption1.setText(relationshipOption_1.getRelationship1());
buttonOption2 = findVIEwByID(R.ID.option2);
buttonOption2.setText(relationshipOption_1.getRelationship2());
Onoption1ClickbuttonListener();
Onoption2ClickbuttonListener();
}
}
// Click Listener action for each option selected
public voID Onoption1ClickbuttonListener() {
buttonOption1.setonClickListener(new VIEw.OnClickListener() {
@OverrIDe
public voID onClick(VIEw v) {
if (relationshipOption_1.getCorrectRelationship() == 1) { // If correct,click next to go to next qn if any
AlertDialog.Builder correct = new AlertDialog.Builder(PeopleModeActivity.this);
correct.setMessage("You got it correct! \n Good Job!").setNeutralbutton("Next",new DialogInterface.OnClickListener() {
@OverrIDe
public voID onClick(DialogInterface dialog,int which) {
dialog.cancel();
Intent peopleMode_intent = new Intent(PeopleModeActivity.this,PeopleModeActivity.class);
peopleMode_intent.putExtra("PEOPLEMODE",PEOPLEMODE);
peopleMode_intent.putExtra("relativeS_ID",(relativeS_ID + 1));
startActivity(peopleMode_intent);
overrIDePendingTransition(0,0);
}
}).setCancelable(false);
AlertDialog alert_2 = correct.create();
correct.show();
}
if (relationshipOption_1.getCorrectRelationship() == 0) { // If wrong,same question will be repeated
AlertDialog.Builder wrong = new AlertDialog.Builder(PeopleModeActivity.this);
wrong.setMessage("No,not correct! \n It's okay,Try Again!").setNeutralbutton("Do again",relativeS_ID); // relatives_ID (Question ID) will stay the same since question will be repeated
startActivity(peopleMode_intent);
overrIDePendingTransition(0,0);
}
}).setCancelable(false);
AlertDialog alert_2 = wrong.create();
wrong.show();
}
}
});
}
public voID Onoption2ClickbuttonListener() {
buttonOption2.setonClickListener(new VIEw.OnClickListener() {
@OverrIDe
public voID onClick(VIEw v) {
if (relationshipOption_2.getCorrectRelationship() == 1) { // If correct,0);
}
}).setCancelable(false);
AlertDialog alert_2 = correct.create();
correct.show();
}
if (relationshipOption_2.getCorrectRelationship() == 0) { // If wrong,0);
}
}).setCancelable(false);
AlertDialog alert_2 = wrong.create();
wrong.show();
}
}
});
}
}
public class sqliteDbHandler extends sqliteOpenHelper {
public static final int sqlITEDB_VERSION = 1;
public static final String sqlITEDB_name = "fyp.db";
// PatIEnt Details
public static final String PatIEnt_Details_table = "PatIEntDetails";
public static final String PatIEnt_Details_Column_ID = "ID";
public static final String PatIEnt_Details_Column_name = "name";
// PatIEnts' relatives (Question for "People" Game Mode)
public static final String PatIEntDetails_relatives_table = "PatIEntDetails_relatives";
public static final String PatIEntDetails_relatives_Column_relativesID = "relativesID";
public static final String PatIEntDetails_relatives_Column_PatIEntID = "PatIEntID";
public static final String PatIEntDetails_relatives_Column_name = "name";
public static final String PatIEntDetails_relatives_Column_Photo = "Photo";
// PatIEnts' Relationships with relatives (Answer for "People" Game Mode)
public static final String PatIEntDetails_relatives_Relationships_table = "PatIEntDetails_relatives_Relationships";
public static final String PatIEntDetails_relatives_Relationships_Column_RelationshipID = "RelationshipID";
public static final String PatIEntDetails_relatives_Relationships_Column_relativesID = "relativesID";
public static final String PatIEntDetails_relatives_Relationships_Column_Relationship = "Relationship";
public static final String PatIEntDetails_relatives_Relationships_Column_CorrectRelationship = "CorrectRelationship";
public sqliteDbHandler(Context context) {
super(context,sqlITEDB_name,null,sqlITEDB_VERSION);
}
// Populate database with data to support "People" Game Mode
@OverrIDe
public voID onCreate (sqliteDatabase db) {
// Create table in preetifyp.db database for PatIEnt Details
String PATIENT_DETAILS = "CREATE table " + PatIEnt_Details_table + "("
+ PatIEnt_Details_Column_ID + " INTEGER PRIMARY KEY autoINCREMENT,"
+ PatIEnt_Details_Column_name + " TEXT" + ")";
db.execsql(PATIENT_DETAILS);
// Create table in preetifyp.db database for PatIEnts' relatives (Questions for "People" Game Mode)
String PATIENTDETAILS_relativeS = "CREATE table " + PatIEntDetails_relatives_table + " ( "
+ PatIEntDetails_relatives_Column_relativesID + " INTEGER PRIMARY KEY autoINCREMENT,"
+ PatIEntDetails_relatives_Column_PatIEntID + " INTEGER,"
+ PatIEntDetails_relatives_Column_name + " TEXT,"
+ PatIEntDetails_relatives_Column_Photo + " TEXT," // testing with TEXT to get the quiz running,change to INTEGER later
+ " FOREIGN KEY( " + PatIEntDetails_relatives_Column_PatIEntID + " ) REFERENCES " + PatIEnt_Details_table
+ " ( " + PatIEnt_Details_Column_ID + " ) )";
db.execsql(PATIENTDETAILS_relativeS);
// Create table in preetifyp.db database for PatIEnts' Relationships with relatives (Answers for "People" Game Mode)
String PATIENTDETAILS_relativeS_RELATIONSHIPS = "CREATE table " + PatIEntDetails_relatives_Relationships_table + " ( "
+ PatIEntDetails_relatives_Relationships_Column_RelationshipID + " INTEGER PRIMARY KEY autoINCREMENT,"
+ PatIEntDetails_relatives_Relationships_Column_relativesID + " INTEGER,"
+ PatIEntDetails_relatives_Relationships_Column_Relationship + " TEXT,"
+ PatIEntDetails_relatives_Relationships_Column_CorrectRelationship + " INTEGER," // Responses: 0 = no,1 = yes
+ " FOREIGN KEY( " + PatIEntDetails_relatives_Relationships_Column_relativesID + " ) REFERENCES " + PatIEntDetails_relatives_table
+ " ( " + PatIEntDetails_relatives_Column_relativesID + " ) )";
db.execsql(PATIENTDETAILS_relativeS_RELATIONSHIPS);
// Insert data for "People" Game Mode
// Insert PatIEnt Details data
db.execsql("INSERT INTO " + PatIEnt_Details_table + " VALUES (" + 1 + ",'Sandra' )");
db.execsql("INSERT INTO " + PatIEnt_Details_table + " VALUES (" + 2 + ",'Tom' )");
// Insert PatIEnts' relatives data (Questions)
db.execsql("INSERT INTO " + PatIEntDetails_relatives_table + " VALUES (" + 1 + "," + 1 + ",'john','photo of john' )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_table + " VALUES (" + 2 + ",'susan','photo of susan' )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_table + " VALUES (" + 3 + ",'mary','photo of mary' )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_table + " VALUES (" + 4 + ",'Sarah','photo of Sarah' )" );
// Insert PatIEnts' relatives' Relationships data (Answers)
// First Question's Answer - John
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 1 + ",'Father',+ 1 )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 2 + ",+ 0 )" );
// Second Question's Answer - Susan
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 3 + "," + 2 + ",+ 0 )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 4 + ",'Mother',+ 1 )" );
// Third Question's Answer - Mary
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 5 + "," + 3 + ",'Sister',+ 1 )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 6 + ",'FrIEnd',+ 0 )" );
// Fourth Question's Answer - Sarah
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 7 + "," + 4 + ",+ 0 )" );
db.execsql("INSERT INTO " + PatIEntDetails_relatives_Relationships_table + " VALUES (" + 8 + ",+ 1 )" );
}
public voID addPhotos(PeopleModeQuestions photo){
sqliteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(PatIEntDetails_relatives_Column_Photo,photo.getPhoto()); // Photo path
// Inserting photo
db.insert(PatIEntDetails_relatives_table,values);
db.close();
}
// Return all patIEnt names stored in database
public List<String> getAllPatIEntnames() {
List<String> patIEnts = new ArrayList<String>();
// Select PatIEnt names data from table
String selectPatIEntnames = "SELECT " + PatIEnt_Details_Column_name + " FROM " + PatIEnt_Details_table;
sqliteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawquery(selectPatIEntnames,null);
// looPing through all rows and adding to List
if(cursor!=null && cursor.getCount() > 0) {
if (cursor.movetoFirst()) {
do {
patIEnts.add(cursor.getString(0));
} while (cursor.movetoNext());
}
}
cursor.close();
db.close();
return patIEnts;
}
public List<PeopleModeQuestions> getAllPeopleModeQuestions() {
List<PeopleModeQuestions> listofrelativesPhotos = new ArrayList<PeopleModeQuestions>();
String selectAllrelativesPhotos = "SELECT " + PatIEntDetails_relatives_Column_Photo + " FROM " + PatIEntDetails_relatives_table;
sqliteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawquery(selectAllrelativesPhotos,null);
// looPing through all rows and adding relatives' photos (all questions) to List
if(cursor!=null && cursor.getCount() > 0) {
if (cursor.movetoFirst()) {
do {
PeopleModeQuestions qn = new PeopleModeQuestions();
qn.setPhoto(cursor.getString(cursor.getColumnIndex(PatIEntDetails_relatives_Column_Photo)));
listofrelativesPhotos.add(qn);
} while (cursor.movetoNext());
}
}
cursor.close();
db.close();
return listofrelativesPhotos;
}
// get current relative's photo (current question)
public PeopleModeQuestions getrelativesPhotoQuestion(int relatives_ID) {
// Select relative's Photo data from table (questions)
String selectcurrentrelativesPhoto = "SELECT " + PatIEntDetails_relatives_Column_Photo + " FROM " + PatIEntDetails_relatives_table
+ " WHERE " + PatIEntDetails_relatives_Column_relativesID + " = " + relatives_ID;
sqliteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawquery(selectcurrentrelativesPhoto,null);
if(cursor!=null && cursor.getCount() > 0) {
if (cursor.movetoFirst()) {
do {
PeopleModeQuestions qn = new PeopleModeQuestions();
qn.setPhoto(cursor.getString(cursor.getColumnIndex(PatIEntDetails_relatives_Column_Photo)));
//listofrelativesPhotos.add(qn);
} while (cursor.movetoNext());
}
}
cursor.close();
db.close();
//return selectcurrentrelativesPhoto;
return null;
}
// People Mode Answers - PatIEntDetails_relatives_Relationships
public ArrayList <PeopleModeAnswers> getrelativesPhotoAnswersByrelativesID(int relatives_ID) {
ArrayList<PeopleModeAnswers> relationships = new ArrayList<>();
relationships.clear(); // clear ArrayList to allow new relationships answer data to be added
// Select relative's Relationship data from table (answers)
String selectrelativesPhotoAnswersByrelativesID = "SELECT " + PatIEntDetails_relatives_Relationships_Column_Relationship + " FROM " + PatIEntDetails_relatives_Relationships_table
+ " WHERE " + PatIEntDetails_relatives_Relationships_Column_relativesID + " = " + relatives_ID;
sqliteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawquery(selectrelativesPhotoAnswersByrelativesID,null);
// looPing through all rows and adding relationships (answers) to ArrayList
if(cursor!=null && cursor.getCount() > 0) {
if (cursor.movetoFirst()) {
do {
PeopleModeAnswers answers = new PeopleModeAnswers();
answers.setRelationship1(cursor.getString(cursor.getColumnIndex(PatIEntDetails_relatives_Relationships_Column_Relationship)));
answers.setRelationship2(cursor.getString(cursor.getColumnIndex(PatIEntDetails_relatives_Relationships_Column_Relationship)));
relationships.add(answers);
} while (cursor.movetoNext());
}
}
cursor.close();
db.close();
return relationships;
}
@OverrIDe
public voID onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
if (oldVersion != newVersion) {
db.execsql("DROP table IF EXISTS " + PatIEnt_Details_table);
db.execsql("DROP table IF EXISTS " + PatIEntDetails_relatives_table);
db.execsql("DROP table IF EXISTS " + PatIEntDetails_relatives_Relationships_table);
// create tables again
onCreate(db);
}
}
@OverrIDe
public voID onConfigure(sqliteDatabase db) {
db.setForeignKeyConstraintsEnabled(true);
super.onConfigure(db);
}
}
PeopleModeQuestions 类
2021-04-28 03:28:52.702 5617-5617/com.example.memorydementia E/AndroIDRuntime: FATAL EXCEPTION: main
Process: com.example.memorydementia,PID: 5617
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.memorydementia/com.example.memorydementia.PeopleModeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.memorydementia.PeopleModeQuestions.getPhoto()' on a null object reference
at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:3449)
at androID.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at androID.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at androID.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at androID.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at androID.os.Handler.dispatchMessage(Handler.java:106)
at androID.os.Looper.loop(Looper.java:223)
at androID.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.androID.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.memorydementia.PeopleModeQuestions.getPhoto()' on a null object reference
at com.example.memorydementia.PeopleModeActivity.onCreate(PeopleModeActivity.java:97)
at androID.app.Activity.performCreate(Activity.java:8000)
at androID.app.Activity.performCreate(Activity.java:7984)
at androID.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:3422)
at androID.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at androID.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at androID.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at androID.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at androID.os.Handler.dispatchMessage(Handler.java:106)
at androID.os.Looper.loop(Looper.java:223)
at androID.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.androID.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:947)
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