我为我的应用程序使用SQLite数据库，我想将来自多个活动的数据保存到一个表中。在第一个活动中，我使用add方法在表中创建一行。在下一个活动中，我将使用update方法更新现有行中的列。
我使用DB Browser for SQLite应用程序检查我的数据库，它显示我从第二次活动保存的数据不在数据库中（空）。我不知道出什么问题了。
这是我的课程：
SQLiteHelper：
public class SQLiteHelper extends SQLiteOpenHelper implements ProjectDAO {
public SQLiteHelper(Context context) {
super(context, "my_db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
try {
db.execSQL("CREATE TABLE tbl_project_info (id INTEGER PRIMARY KEY," +
"name TEXT," +
"company_name TEXT," +
"address TEXT," +
"length1 TEXT," +
"length2 TEXT," +
"length3 TEXT," +
"length4 TEXT," +
"length5 TEXT," +
"diameter1 Text,"+
"diameter2 Text,"+
"diameter3 Text,"+
"diameter4 Text,"+
"diameter5 Text)");
} catch (SQLiteException e) {
Log.e("SQLITE", "onCreate: " + e.toString());
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
@Override
public boolean addProject(Project project) {
SQLiteDatabase db = getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("name", project.getName());
contentValues.put("company_name", project.getCompany_name());
contentValues.put("address", project.getAddress());
contentValues.put("length1",project.getLength1());
contentValues.put("length2",project.getLength2());
contentValues.put("length3",project.getLength3());
contentValues.put("length4",project.getLength4());
contentValues.put("length5",project.getLength5());
contentValues.put("diameter1",project.getDiameter1());
contentValues.put("diameter2",project.getDiameter2());
contentValues.put("diameter3",project.getDiameter3());
contentValues.put("diameter4",project.getDiameter4());
contentValues.put("diameter5",project.getDiameter5());
long result = db.insert("tbl_project_info", null, contentValues);
db.close();
return result != -1;
}
@Override
public int getProjectsCount() {
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM tbl_project_info", null);
int count = cursor.getCount();
cursor.close();
db.close();
return count;
}
@Override
public boolean updateProject(Project project) {
SQLiteDatabase db = getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("length1",project.getLength1());
contentValues.put("length2",project.getLength2());
contentValues.put("length3",project.getLength3());
contentValues.put("length4",project.getLength4());
contentValues.put("length5",project.getLength5());
contentValues.put("diameter1",project.getDiameter1());
contentValues.put("diameter2",project.getDiameter2());
contentValues.put("diameter3",project.getDiameter3());
contentValues.put("diameter4",project.getDiameter4());
contentValues.put("diameter5",project.getDiameter5());
db.update("tbl_project_info",contentValues,"id = ?", new String[]{String.valueOf(project.getId())});
db.close();
return true;
}
@Override
public List<Project> getAllProjects() {
List<Project> projects = new ArrayList<>();
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM tbl_project_info", null);
if (cursor.moveToFirst()) {
do {
Project project = new Project();
project.setName(cursor.getString(0));
project.setCompany_name(cursor.getString(1));
project.setAddress(cursor.getString(2));
projects.add(project);
} while (cursor.moveToNext());
}
return projects;
}
}
NewProjectActivity：
public class NewProjectActivity extends AppCompatActivity {
private ProjectDAO projectDAO;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_new_project);
projectDAO = DBInjector.provideProjectDao(this);
setupViews();
}
private void setupViews() {
final EditText projectNameET = findViewById(R.id.et_newProject_projectName);
final EditText companyNameET = findViewById(R.id.et_newProject_companyName);
final EditText addressET = findViewById(R.id.et_newProject_address);
Button saveInfoBTN = findViewById(R.id.btn_newProject_saveInfo);
saveInfoBTN.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (projectNameET.length() > 0) {
if (companyNameET.length() > 0) {
if (addressET.length() > 0) {
Project project = new Project();
project.setName(projectNameET.getText().toString());
project.setCompany_name(companyNameET.getText().toString());
project.setAddress(addressET.getText().toString());
if (projectDAO.addProject(project)){
Toast.makeText(NewProjectActivity.this, "Success", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(NewProjectActivity.this, "Failed", Toast.LENGTH_SHORT).show();
}
}
}
}
Intent intent = new Intent(NewProjectActivity.this,MainActivity.class);
startActivity(intent);
}
});
}
}
主要活动 ：
public class MainActivity extends AppCompatActivity {
private ProjectDAO projectDAO;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
projectDAO = DBInjector.provideProjectDao(this);
final EditText lengthET1 = findViewById(R.id.et_main_length1);
final EditText lengthET2 = findViewById(R.id.et_main_length2);
final EditText lengthET3 = findViewById(R.id.et_main_length3);
final EditText lengthET4 = findViewById(R.id.et_main_length4);
final EditText lengthET5 = findViewById(R.id.et_main_length5);
final EditText diameterET1 = findViewById(R.id.et_main_diameter1);
final EditText diameterET2 = findViewById(R.id.et_main_diameter2);
final EditText diameterET3 = findViewById(R.id.et_main_diameter3);
final EditText diameterET4 = findViewById(R.id.et_main_diameter4);
final EditText diameterET5 = findViewById(R.id.et_main_diameter5);
Button calculateButton = findViewById(R.id.btn_main_calculate);
calculateButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
float Le1 = 0;
if (lengthET1.length() > 0) {
String L1 = lengthET1.getText().toString();
Le1 = Float.parseFloat(L1);
}
float Di1 = 0;
if (diameterET1.length() > 0) {
String D1 = diameterET1.getText().toString();
Di1 = Float.parseFloat(D1);
}
float Le2 = 0;
if (lengthET2.length() > 0) {
String L2 = lengthET2.getText().toString();
Le2 = Float.parseFloat(L2);
}
float Di2 = 0;
if (diameterET2.length() > 0) {
String D2 = diameterET2.getText().toString();
Di2 = Float.parseFloat(D2);
}
float Le3 = 0;
if (lengthET3.length() > 0) {
String L3 = lengthET3.getText().toString();
Le3 = Float.parseFloat(L3);
}
float Di3 = 0;
if (diameterET3.length() > 0) {
String D3 = diameterET3.getText().toString();
Di3 = Float.parseFloat(D3);
}
float Le4 = 0;
if (lengthET4.length() > 0) {
String L4 = lengthET4.getText().toString();
Le4 = Float.parseFloat(L4);
}
float Di4 = 0;
if (diameterET4.length() > 0) {
String D4 = diameterET4.getText().toString();
Di4 = Float.parseFloat(D4);
}
float Le5 = 0;
if (lengthET5.length() > 0) {
String L5 = lengthET5.getText().toString();
Le5 = Float.parseFloat(L5);
}
float Di5 = 0;
if (diameterET5.length() > 0) {
String D5 = diameterET5.getText().toString();
Di5 = Float.parseFloat(D5);
}
final float Surface1 = (float) (Le1 * Di1 * Math.PI);
final float Surface2 = (float) (Le2 * Di2 * Math.PI);
final float Surface3 = (float) (Le3 * Di3 * Math.PI);
final float Surface4 = (float) (Le4 * Di4 * Math.PI);
final float Surface5 = (float) (Le5 * Di5 * Math.PI);
final float Surface = Surface1 + Surface2 + Surface3 + Surface4 + Surface5;
Intent intent = new Intent(MainActivity.this, IntensityActivity.class);
if (Surface == 0) {
Toast.makeText(MainActivity.this, "No numbers are entered", Toast.LENGTH_SHORT).show();
} else {
intent.putExtra("Result", Surface);
startActivity(intent);
}
PersonalInfoSharedPrefManager manager = new PersonalInfoSharedPrefManager(MainActivity.this);
manager.setSuface(Surface);
Project project = new Project();
project.setLength1(lengthET1.getText().toString());
project.setDiameter1(diameterET1.getText().toString());
project.setLength2(lengthET2.getText().toString());
project.setDiameter2(diameterET2.getText().toString());
project.setLength3(lengthET3.getText().toString());
project.setDiameter3(diameterET3.getText().toString());
project.setLength4(lengthET4.getText().toString());
project.setDiameter4(diameterET4.getText().toString());
project.setLength5(lengthET5.getText().toString());
project.setDiameter5(diameterET5.getText().toString());
projectDAO.updateProject(project);
}
});
}
}
最佳答案
您的updateProject方法粗略地说是更新值（根据Contentvalues），其中项目ID是从项目的getID方法返回的值。
但是，当您创建要传递给该方法的项目时，您没有提供ID（它应与数据库中添加的行一致），因此它将是一些任意值，可能为null（不能说为Project类）不包含在您的代码中。）
这就是原因。
可能有许多修复。一种方法是获取ID（非常可取/标准的方法是，标识行是使用ID列的原因）。
如果将项目添加到数据库中，则可以通过以下方法来检索该方法：如果SQLiteDatabase方法返回-1（而不是返回值）（插入行的ID），则返回false。然后，您可以检查它是否为-1或小于1（id将为1或更大），这表明未添加该行。如果该值为1或更大，则表明该行已插入。
然后，您可以通过IntentExtra将ID传递给MainActivity，在其中提取项目ID并将其设置为该值。请注意，理想情况下，您应该为id使用较长的ID，因为它最多可以是64位带符号的整数（通常是1，2，3然后以此类推……）。
另一种方法是根据可以唯一标识项目的其他已知存储值从数据库中标识项目，然后更改updateProject方法的WHERE子句（第3和第4个参数）。
另一种方法是使用标识信息提取ID（因此是上述排列方式）
建议的修复
请注意，这是原理代码，尚未经过测试，因此可能包含一些错误：
已包含注释以标识更改。他们通常会被//<<<<跟随一些已经完成的指示。
1）修改addProject方法以返回id else -1：-
@Override
public long addProject(Project project) { //<<<< CHANGED
SQLiteDatabase db = getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("name", project.getName());
contentValues.put("company_name", project.getCompany_name());
contentValues.put("address", project.getAddress());
contentValues.put("length1",project.getLength1());
contentValues.put("length2",project.getLength2());
contentValues.put("length3",project.getLength3());
contentValues.put("length4",project.getLength4());
contentValues.put("length5",project.getLength5());
contentValues.put("diameter1",project.getDiameter1());
contentValues.put("diameter2",project.getDiameter2());
contentValues.put("diameter3",project.getDiameter3());
contentValues.put("diameter4",project.getDiameter4());
contentValues.put("diameter5",project.getDiameter5());
long result = db.insert("tbl_project_info", null, contentValues);
db.close();
return result; //<<<< CHANGED
}
2）传递来自NewProjectActivity的id为MainActivity：
saveInfoBTN.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
long projectid = -1; //<<<< LINE ADDED
if (projectNameET.length() > 0) {
if (companyNameET.length() > 0) {
if (addressET.length() > 0) {
Project project = new Project();
project.setName(projectNameET.getText().toString());
project.setCompany_name(companyNameET.getText().toString());
project.setAddress(addressET.getText().toString());
projectid = projectDAO.addProject(project); //<<<< LINE ADDED
if (projectid > 0){ //<<<< LINE CHANGED
Toast.makeText(NewProjectActivity.this, "Success", Toast.LENGTH_SHORT).show();
}else {
Toast.makeText(NewProjectActivity.this, "Failed", Toast.LENGTH_SHORT).show();
}
}
}
}
Intent intent = new Intent(NewProjectActivity.this,MainActivity.class);
intent.putExtra("IE_PROJECTID",projectid); //<<<< ADDED
startActivity(intent);
}
});
}
3）在MainActivity中检索ID：
private long mProjectID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
projectDAO = DBInjector.provideProjectDao(this);
//<<<< ADDED folowing lines to get the id from the intent >>>>
mProjectID = getIntent().getLongExtra(
"IE_PROJECTID",
0 //<<<< NOTE default could be -1 (or any negative) as long as it's less than 1
);
.........
project.setID(mProjectID); //<<<< ADDED might need setter in project
projectDAO.updateProject(project);
可以用常量代替“ IE_PROJECTID”的使用，还有一些可以使用的库存，例如
Intent.EXTRA_?????????（其中?????????代表很多值）关于android - SQLite数据库列无法使用Update方法更新，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/49596441/