这是我第一次使用stackoverflow.com发布问题。我关心的问题是，每当我点击此页面时出现错误。当我在新活动上测试它时，编码完全正常没有任何问题，但是当我测试我的最后一年项目时，我目前正在为客户的需求进行测试，并且每次点击该活动页面时它都会崩溃。我是android工作室的新手，对android studio不熟悉。希望你们能解决这个问题，非常感谢你们！到目前为止，这是我的编码和错误：
Logcat错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.student.amanvilleapp, PID: 5722
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.student.amanvilleapp/com.example.student.amanvilleapp.event}: android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:808)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:793)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:696)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:671)
at com.example.student.amanvilleapp.DBMain.openDB(DBMain.java:114)
at com.example.student.amanvilleapp.event.onCreate(event.java:76)
at android.app.Activity.performCreate(Activity.java:6662)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
event.java：
public class event extends AppCompatActivity {
String DB_PATH;
final Context context=this;
private SQLiteDatabase mDataBase;
private static String DB_NAME ="Banking.db";
TextView txt;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_event);
Toolbar myToolbar = (Toolbar) findViewById(R.id.toolbar);
myToolbar.setTitle("EVENTS & NEWS");
setSupportActionBar(myToolbar);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
txt=(TextView)findViewById(R.id.txt);
DBMain db;
db = new DBMain(this);
try {
db.createDB();
} catch (IOException ioe) {
throw new Error("Database not created....");
}
try {
db.openDB();
}catch(SQLException sqle){
throw sqle;
}
SQLiteDatabase db1;
db1=openOrCreateDatabase("Banking",SQLiteDatabase.CREATE_IF_NECESSARY,null);
Cursor c= db1.rawQuery("SELECT * FROM bank",null);
c.moveToFirst();
String temp="";
while(! c.isAfterLast())
{
String s2=c.getString(0);
String s3=c.getString(1);
String s4=c.getString(2);
temp=temp+"\n Id:"+s2+"\tType:"+s3+"\tBal:"+s4;
c.moveToNext();
}
txt.setText(temp);
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu2, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.home:
Intent intent = new Intent();
intent.setClass(event.this, MainActivity.class);
event.this.startActivity(intent);
return true;
case R.id.about:
Intent intent1 = new Intent();
intent1.setClass(event.this, aboutus.class);
event.this.startActivity(intent1);
return true;
case R.id.pricing:
Intent intent3 = new Intent();
intent3.setClass(event.this, pricing.class);
event.this.startActivity(intent3);
return true;
case R.id.contact:
Intent intent4 = new Intent();
intent4.setClass(event.this, contact.class);
event.this.startActivity(intent4);
return true;
case R.id.rateus:
Intent intent5 = new Intent();
intent5.setClass(event.this, rateus.class);
event.this.startActivity(intent5);
return true;
case R.id.aboutapp:
LayoutInflater factory = LayoutInflater.from(event.this);
final View view = factory.inflate(R.layout.aboutapp, null);
AlertDialog alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle("About This App");
alertDialog.setMessage("App Version: 1.0" + "\n" + "\n"
+ "App name: AmanVilleApp" + "\n" + "\n" + "This app is design by Jasper Koay Chin Loong for Sentral College Penang's Final Year Project.");
alertDialog.setButton("OK", new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int which)
{
//TODO Auto-generated method stub
}
});
alertDialog.show();
return true;
case R.id.exit:
moveTaskToBack(true);
android.os.Process.killProcess(android.os.Process.myPid());
System.exit(1);
default:
return super.onOptionsItemSelected(item);
}
}
}
DBMain.java
public class DBMain extends SQLiteOpenHelper {
private static String DB_PATH=
"data/data/com.example.dbimportfin/databases/";
private static String DB_NAME = "Banking";
private SQLiteDatabase dbObj;
private final Context context;
public DBMain(Context context) {
super(context, DB_NAME , null, 3);
this. context = context;
}
public void createDB() throws IOException {
this.getReadableDatabase();
Log.i("Readable ends....................","end");
try {
copyDB();
Log.i("copy db ends....................","end");
} catch (IOException e) {
throw new Error("Error copying database");
}
}
private boolean checkDB(){
SQLiteDatabase checkDB = null;
try{
String path = DB_PATH + DB_NAME;
Log.i("myPath ......",path);
checkDB = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
Log.i("myPath ......",path);
if (checkDB!=null)
{
Cursor c= checkDB.rawQuery("SELECT * FROM bank", null);
Log.i("Cursor.......",c.getString(0));
c.moveToFirst();
String contents[]=new String[80];
int flag=0;
while(! c.isAfterLast())
{
String temp="";
String s2=c.getString(0);
String s3=c.getString(1);
String s4=c.getString(2);
temp=temp+"\n Id:"+s2+"\tType:"+s3+"\tBal:"+s4;
contents[flag]=temp;
flag=flag+1;
Log.i("DB values.........",temp);
c.moveToNext();
}
}
else
{
return false;
}
}catch(SQLiteException e){
e.printStackTrace();
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
public void copyDB() throws IOException{
try {
Log.i("inside copyDB....................","start");
InputStream ip = context.getAssets().open(DB_NAME+".db");
Log.i("Input Stream....",ip+"");
String op= DB_PATH + DB_NAME ;
OutputStream output = new FileOutputStream( op);
byte[] buffer = new byte[1024];
int length;
while ((length = ip.read(buffer))>0){
output.write(buffer, 0, length);
Log.i("Content.... ",length+"");
}
output.flush();
output.close();
ip.close();
}
catch (IOException e) {
Log.v("error", e.toString());
}
}
public void openDB() throws SQLException {
String myPath = DB_PATH + DB_NAME;
dbObj = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
Log.i("open DB......",dbObj.toString());
}
@Override
public synchronized void close() {
if(dbObj != null)
dbObj.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
The activity that should show like this
And this is the image that I put my code on the existing project I created not long ago
答案 0 :(得分：1)
添加Manifest可能不适用于API 23及更高版本。运行应用程序时请求许可：
从Android 6.0（API级别23）开始，用户授予权限 应用程序运行时的应用程序，而非安装应用程序时的应用程序。这个 方法简化了应用安装过程，因为用户没有 需要在安装或更新应用时授予权限。
String[] permissions = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
requestPermissions(permissions, WRITE_REQUEST_CODE);
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case WRITE_REQUEST_CODE:
if(grantResults[0] == PackageManager.PERMISSION_GRANTED){
//Permission granted.
//Continue with writing files...
}
else{
//Permission denied.
}
break;
}
}
还设置DB_PATH以创建数据库。
SQLiteDatabase.openDatabase(DB_PATH + "\" + DB_NAME, null, SQLiteDatabase.OPEN_READWRITE);