Java 将SQLiteDatabase导出到CSV Android Studio
我已经使用这段代码好几天了。我在Java方面没有太多经验，但我可以拼凑我在网上找到的代码并从中学习。我一直在使用这个网站作为我当前活动的模板。我已经对提供的代码做了很多修改，但都是一个接一个的错误。现在使用我的代码，我得到了sqldb（第211行左右…无法解析符号。我只是觉得我没有正确地声明sqldb是我的全部问题。您可能会在网上的其他地方注意到代码的其他部分。只是尝试学习，然后在完成后将代码更改为我需要的代码。这里是一些文件。谢谢你的帮助！（如果你看到任何其他的变化，那将是伟大的，因为我一直在做的就是使用Android Studio的建议）。不确定您需要查看哪些文件，但这里有一些。我的活动是我的主要爱好。在MyActivity.java中选择“send”时，它应导出csv文件 MyActivity.javaJava 将SQLiteDatabase导出到CSV Android Studio,java,android,sqlite,csv,Java,Android,Sqlite,Csv,我已经使用这段代码好几天了。我在Java方面没有太多经验，但我可以拼凑我在网上找到的代码并从中学习。我一直在使用这个网站作为我当前活动的模板。我已经对提供的代码做了很多修改，但都是一个接一个的错误。现在使用我的代码，我得到了sqldb（第211行左右…无法解析符号。我只是觉得我没有正确地声明sqldb是我的全部问题。您可能会在网上的其他地方注意到代码的其他部分。只是尝试学习，然后在完成后将代码更改为我需要的代码。这里是一些文件。谢谢你的帮助！（如果你看到任何其他的变化，那将是伟大的，因为我一直在
package com.nate.nash.howtoloveme;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Environment;
import android.support.annotation.Nullable;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatCallback;
import android.support.v7.app.AppCompatDelegate;
import android.support.v7.view.ActionMode;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
public class MyActivity extends ListActivity implements AppCompatCallback {
private DBHelper dbHelper;
@Override
public void onBackPressed() {
new AlertDialog.Builder(this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Closing Activity")
.setMessage("Are you sure you want to close this activity?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNegativeButton("No", null)
.show();
}
private AppCompatDelegate delegate;
TextView student_Id;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO remove comment code
// TODO change wording from student to feeling
// TODO change when list is removed or added, spinner changes
// TODO start new activity after MainActivity.java
//let's create the delegate, passing the activity at both arguments (Activity, AppCompatCallback)
delegate = AppCompatDelegate.create(this, this);
//we need to call the onCreate() of the AppCompatDelegate
delegate.onCreate(savedInstanceState);
//we use the delegate to inflate the layout
delegate.setContentView(R.layout.activity_my);
//TODO custom added
//Finally, let's add the Toolbar
Toolbar toolbar= (Toolbar) findViewById(R.id.my_awesome_toolbar);
delegate.setSupportActionBar(toolbar);
super.onCreate(savedInstanceState);
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if (studentList.size() != 0) {
repo = new StudentRepo(this);
studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MyActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this, "No student!", Toast.LENGTH_SHORT).show();
}
} else {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my_null);
Button button = (Button) findViewById(R.id.angry_btn);
}
String versionName = "";
try {
versionName = getApplicationContext().getPackageManager().getPackageInfo(getApplicationContext().getPackageName(), 0).versionName;
} catch (PackageManager.NameNotFoundException e) {
e.printStackTrace();
}
TextView versionname = (TextView) findViewById(R.id.versionName);
}
public void onCheckboxClicked(View view) {
// Is the view now checked?
boolean checked = ((CheckBox) view).isChecked();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_my, menu);
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
Intent intent = new Intent(MyActivity.this, SettingsActivity.class);
startActivity(intent);
//finish();
return true;
}
if (id == R.id.action_add) {
Intent intent = new Intent(MyActivity.this, MainActivity.class);
startActivity(intent);
return true;
}
if (id == R.id.test) {
Intent intent = new Intent(MyActivity.this, HelloGridView.class);
startActivity(intent);
return true;
}
if (id == R.id.send) {
//main code begins here
try {
SQLiteDatabase sqldb = dbHelper.getReadableDatabase();
Cursor c = null;
c = sqldb.rawQuery("select * from crud.db", null);
int rowcount = 0;
int colcount = 0;
File sdCardDir = Environment.getExternalStorageDirectory();
String filename = "MyBackUp.csv";
// the name of the file to export with
File saveFile = new File(sdCardDir, filename);
FileWriter fw = new FileWriter(saveFile);
BufferedWriter bw = new BufferedWriter(fw);
rowcount = c.getCount();
colcount = c.getColumnCount();
if (rowcount > 0) {
c.moveToFirst();
for (int i = 0; i < colcount; i++) {
if (i != colcount - 1) {
bw.write(c.getColumnName(i) + ",");
} else {
bw.write(c.getColumnName(i));
}
}
bw.newLine();
for (int i = 0; i < rowcount; i++) {
c.moveToPosition(i);
for (int j = 0; j < colcount; j++) {
if (j != colcount - 1)
bw.write(c.getString(j) + ",");
else
bw.write(c.getString(j));
}
bw.newLine();
}
bw.flush();
Toast.makeText(this, "Exported Successfully.", Toast.LENGTH_SHORT).show();
//infotext.setText("Exported Successfully.");
}
} catch (Exception ex) {
if (sqldb.isOpen()) {
try {
sqldb.close();
} catch (IOException e) {
e.printStackTrace();
}
Toast.makeText(this, ex.getMessage().toString(), Toast.LENGTH_SHORT).show();
//infotext.setText(ex.getMessage().toString());
}
} finally {
}
return true;
}
if (id == R.id.array_add) {
Intent intent = new Intent(MyActivity.this, ArraySave.class);
startActivity(intent);
return true;
}
if (id == R.id.action_quit) {
new AlertDialog.Builder(this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Closing Activity")
.setMessage("Are you sure you want to close this activity?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNegativeButton("No", null)
.show();
}
switch(item.getItemId())
{
case R.id.preferences:
{
Intent intent = new Intent();
intent.setClassName(this, "MyPreferenceActivity");
startActivity(intent);
return true;
}
}
return super.onOptionsItemSelected(item);
}
public void ButtonOnClick(View v) {
switch (v.getId() /*to get clicked view id**/) {
case R.id.angry_btn:
Intent intent = new Intent(MyActivity.this, MainActivity.class);
startActivity(intent);
break;
default:
break;
}
}
@Override
public void onSupportActionModeStarted(ActionMode mode) {
}
@Override
public void onSupportActionModeFinished(ActionMode mode) {
}
@Nullable
@Override
public ActionMode onWindowStartingSupportActionMode(ActionMode.Callback callback) {
return null;
}
}
package com.nate.nash.howtoloveme;
/**
* Created by Nash on 1/13/2016.
*/
import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
public class MainActivity extends ListActivity implements android.view.View.OnClickListener{
Button btnAdd,btnGetAll;
TextView student_Id;
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
Intent intent = new Intent(MainActivity.this, MyActivity.class);
startActivity(intent);
finish();
}
return super.onKeyDown(keyCode, event);
}
@Override
public void onClick(View view) {
if (view== findViewById(R.id.btnAdd)){
Intent intent = new Intent(this,StudentDetail.class);
intent.putExtra("student_Id",0);
startActivity(intent);
}else {
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
}
btnAdd = (Button) findViewById(R.id.btnAdd);
btnAdd.setOnClickListener(this);
btnGetAll = (Button) findViewById(R.id.btnGetAll);
btnGetAll.setOnClickListener(this);
}
}
package com.nate.nash.howtoloveme;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Environment;
import android.support.annotation.Nullable;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatCallback;
import android.support.v7.app.AppCompatDelegate;
import android.support.v7.view.ActionMode;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
public class MyActivity extends ListActivity implements AppCompatCallback {
private DBHelper dbHelper;
@Override
public void onBackPressed() {
new AlertDialog.Builder(this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Closing Activity")
.setMessage("Are you sure you want to close this activity?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNegativeButton("No", null)
.show();
}
private AppCompatDelegate delegate;
TextView student_Id;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO remove comment code
// TODO change wording from student to feeling
// TODO change when list is removed or added, spinner changes
// TODO start new activity after MainActivity.java
//let's create the delegate, passing the activity at both arguments (Activity, AppCompatCallback)
delegate = AppCompatDelegate.create(this, this);
//we need to call the onCreate() of the AppCompatDelegate
delegate.onCreate(savedInstanceState);
//we use the delegate to inflate the layout
delegate.setContentView(R.layout.activity_my);
//TODO custom added
//Finally, let's add the Toolbar
Toolbar toolbar= (Toolbar) findViewById(R.id.my_awesome_toolbar);
delegate.setSupportActionBar(toolbar);
super.onCreate(savedInstanceState);
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if (studentList.size() != 0) {
repo = new StudentRepo(this);
studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MyActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this, "No student!", Toast.LENGTH_SHORT).show();
}
} else {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my_null);
Button button = (Button) findViewById(R.id.angry_btn);
}
String versionName = "";
try {
versionName = getApplicationContext().getPackageManager().getPackageInfo(getApplicationContext().getPackageName(), 0).versionName;
} catch (PackageManager.NameNotFoundException e) {
e.printStackTrace();
}
TextView versionname = (TextView) findViewById(R.id.versionName);
}
public void onCheckboxClicked(View view) {
// Is the view now checked?
boolean checked = ((CheckBox) view).isChecked();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_my, menu);
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
Intent intent = new Intent(MyActivity.this, SettingsActivity.class);
startActivity(intent);
//finish();
return true;
}
if (id == R.id.action_add) {
Intent intent = new Intent(MyActivity.this, MainActivity.class);
startActivity(intent);
return true;
}
if (id == R.id.test) {
Intent intent = new Intent(MyActivity.this, HelloGridView.class);
startActivity(intent);
return true;
}
if (id == R.id.send) {
//main code begins here
try {
SQLiteDatabase sqldb = dbHelper.getReadableDatabase();
Cursor c = null;
c = sqldb.rawQuery("select * from crud.db", null);
int rowcount = 0;
int colcount = 0;
File sdCardDir = Environment.getExternalStorageDirectory();
String filename = "MyBackUp.csv";
// the name of the file to export with
File saveFile = new File(sdCardDir, filename);
FileWriter fw = new FileWriter(saveFile);
BufferedWriter bw = new BufferedWriter(fw);
rowcount = c.getCount();
colcount = c.getColumnCount();
if (rowcount > 0) {
c.moveToFirst();
for (int i = 0; i < colcount; i++) {
if (i != colcount - 1) {
bw.write(c.getColumnName(i) + ",");
} else {
bw.write(c.getColumnName(i));
}
}
bw.newLine();
for (int i = 0; i < rowcount; i++) {
c.moveToPosition(i);
for (int j = 0; j < colcount; j++) {
if (j != colcount - 1)
bw.write(c.getString(j) + ",");
else
bw.write(c.getString(j));
}
bw.newLine();
}
bw.flush();
Toast.makeText(this, "Exported Successfully.", Toast.LENGTH_SHORT).show();
//infotext.setText("Exported Successfully.");
}
} catch (Exception ex) {
if (sqldb.isOpen()) {
try {
sqldb.close();
} catch (IOException e) {
e.printStackTrace();
}
Toast.makeText(this, ex.getMessage().toString(), Toast.LENGTH_SHORT).show();
//infotext.setText(ex.getMessage().toString());
}
} finally {
}
return true;
}
if (id == R.id.array_add) {
Intent intent = new Intent(MyActivity.this, ArraySave.class);
startActivity(intent);
return true;
}
if (id == R.id.action_quit) {
new AlertDialog.Builder(this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Closing Activity")
.setMessage("Are you sure you want to close this activity?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNegativeButton("No", null)
.show();
}
switch(item.getItemId())
{
case R.id.preferences:
{
Intent intent = new Intent();
intent.setClassName(this, "MyPreferenceActivity");
startActivity(intent);
return true;
}
}
return super.onOptionsItemSelected(item);
}
public void ButtonOnClick(View v) {
switch (v.getId() /*to get clicked view id**/) {
case R.id.angry_btn:
Intent intent = new Intent(MyActivity.this, MainActivity.class);
startActivity(intent);
break;
default:
break;
}
}
@Override
public void onSupportActionModeStarted(ActionMode mode) {
}
@Override
public void onSupportActionModeFinished(ActionMode mode) {
}
@Nullable
@Override
public ActionMode onWindowStartingSupportActionMode(ActionMode.Callback callback) {
return null;
}
}
package com.nate.nash.howtoloveme;
/**
* Created by Nash on 1/13/2016.
*/
import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
public class MainActivity extends ListActivity implements android.view.View.OnClickListener{
Button btnAdd,btnGetAll;
TextView student_Id;
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
Intent intent = new Intent(MainActivity.this, MyActivity.class);
startActivity(intent);
finish();
}
return super.onKeyDown(keyCode, event);
}
@Override
public void onClick(View view) {
if (view== findViewById(R.id.btnAdd)){
Intent intent = new Intent(this,StudentDetail.class);
intent.putExtra("student_Id",0);
startActivity(intent);
}else {
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
StudentRepo repo = new StudentRepo(this);
ArrayList<HashMap<String, String>> studentList = repo.getStudentList();
if(studentList.size()!=0) {
ListView lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
student_Id = (TextView) view.findViewById(R.id.student_Id);
String studentId = student_Id.getText().toString();
Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
objIndent.putExtra("student_Id", Integer.parseInt( studentId));
startActivity(objIndent);
}
});
ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
setListAdapter(adapter);
}else{
Toast.makeText(this,"No student!",Toast.LENGTH_SHORT).show();
}
btnAdd = (Button) findViewById(R.id.btnAdd);
btnAdd.setOnClickListener(this);
btnGetAll = (Button) findViewById(R.id.btnGetAll);
btnGetAll.setOnClickListener(this);
}
}
package com.nate.nash.howtoloveme；
/**
*由Nash于2016年1月13日创建。
*/
导入android.app.ListActivity；
导入android.content.Intent；
导入android.os.Bundle；
导入android.view.KeyEvent；
导入android.view.view；
导入android.widget.AdapterView；
导入android.widget.Button；
导入android.widget.ListAdapter；
导入android.widget.ListView；
导入android.widget.simpledapter；
导入android.widget.TextView；
导入android.widget.Toast；
导入java.util.ArrayList；
导入java.util.HashMap；
公共类MainActivity扩展ListActivity实现android.view.view.OnClickListener{
按钮btnAdd，BTN高度；
TextView学生Id；
@凌驾
公共布尔onKeyDown（int-keyCode，KeyEvent事件）{
if（（keyCode==KeyEvent.keyCode\u BACK））{
意向意向=新意向（MainActivity.this、MyActivity.class）；
星触觉（意向）；
完成（）；
}
返回super.onKeyDown（keyCode，event）；
}
@凌驾
公共void onClick（视图）{
if（视图==findViewById（R.id.btnAdd））{
意向意向=新意向（此，StudentDetail.class）；
intent.putExtra（“学生Id”，0）；
星触觉（意向）；
}否则{
StudentRepo=新StudentRepo（本）；
ArrayList studentList=repo.getStudentList（）；
如果（studentList.size（）！=0）{
ListView lv=getListView（）；
lv.setOnItemClickListener（新的AdapterView.OnItemClickListener（）{
@凌驾
public void onItemClick（AdapterView父对象、视图、整型位置、长id）{
student\u Id=（TextView）view.findViewById（R.Id.student\u Id）；
String studentId=student_Id.getText（）.toString（）；
Intent objIndent=newintent（getApplicationContext（），StudentDetail.class）；
objIndent.putExtra（“student_Id”，Integer.parseInt（studentId））；
星形触觉（明显）；
}
});
ListAdapter=new SimpleAdapter（MainActivity.this，studentList，R.layout.view_student_条目，新字符串[]{“id”，“name”}，新int[]{R.id.student_id，R.id.student_name}）；
setListAdapter（适配器）；
}否则{
Toast.makeText（这个“没有学生！”，Toast.LENGTH_SHORT.show（）；
}
}
}
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
StudentRepo=新StudentRepo（本）；
ArrayList studentList=repo.getStudentList（）；
如果（studentList.size（）！=0）{
ListView lv=getListView（）；
lv.setOnItemClickListener（新的AdapterView.OnItemClickListener（）{
@凌驾
public void onItemClick（AdapterView父对象、视图、整型位置、长id）{
student\u Id=（TextView）view.findViewById（R.Id.student\u Id）；
String studentId=student_Id.getText（）.toString（）；
Intent objIndent=newintent（getApplicationContext（），StudentDetail.class）；
objIndent.putExtra（“student_Id”，Integer.parseInt（studentId））；
星形触觉（明显）；
}
});
ListAdapter=new SimpleAdapter（MainActivity.this，studentList，R.layout.view_student_条目，新字符串[]{“id”，“name”}，新int[]{R.id.student_id，R.id.student_name}）；
setListAdapter（适配器）；
}否则{
Toast.makeText（这个“没有学生！”，Toast.LENGTH_SHORT.show（）；
}
btnAdd=（按钮）findviewbyd（R.id.btnAdd）；
btnAdd.setOnClickListener（此）；
btngeall=（按钮）findViewById（R.id.btngeall）；
btnGetAll.setOnClickListener（此）；
}
}
private void exportDB() {
File dbFile=getDatabasePath("MyDBName.db");
DBHelper dbhelper = new DBHelper(getApplicationContext());
File exportDir = new File(Environment.getExternalStorageDirectory(), "");
if (!exportDir.exists())
{
exportDir.mkdirs();
}
File file = new File(exportDir, "csvname.csv");
try
{
file.createNewFile();
CSVWriter csvWrite = new CSVWriter(new FileWriter(file));
SQLiteDatabase db = dbhelper.getReadableDatabase();
Cursor curCSV = db.rawQuery("SELECT * FROM contacts",null);
csvWrite.writeNext(curCSV.getColumnNames());
while(curCSV.moveToNext())
{
//Which column you want to exprort
String arrStr[] ={curCSV.getString(0),curCSV.getString(1), curCSV.getString(2)};
csvWrite.writeNext(arrStr);
}
csvWrite.close();
curCSV.close();
}
catch(Exception sqlEx)
{
Log.e("MainActivity", sqlEx.getMessage(), sqlEx);
}
}
我使用了你的建议，实际上我以前也尝试过，但在CSVwriter上遇到了问题。事实证明，这是一个需要添加的依赖项。这对我来说是新鲜事！但到目前为止没有错误……所以希望这能让我走上正确的方向！非常感谢。