无法实例化应用程序java.lang.RuntimeException:…BackupDB无法强制转换为android.app.application
舱单：（部分视图） MainActivity，程序立即终止并在日志中发出消息。 它应该已经开始显示按钮来选择继续执行的选项。 在对这个论坛进行了几天的研究之后，我发现一些帖子建议将BackupDb放在清单中的应用程序中。 完成后，我在日志中看到了消息。无法实例化应用程序java.lang.RuntimeException:…BackupDB无法强制转换为android.app.application,java,android,android-intent,Java,Android,Android Intent,舱单：（部分视图） MainActivity，程序立即终止并在日志中发出消息。 它应该已经开始显示按钮来选择继续执行的选项。 在对这个论坛进行了几天的研究之后，我发现一些帖子建议将BackupDb放在清单中的应用程序中。 完成后，我在日志中看到了消息。 在用尽我的研究场地之后，我想知道可能存在什么问题以及如何解决它 舱单：（部分视图） 备份数据库：将数据库复制到SD卡 package com.peter.databasetest; import java.io.File; import ja
在用尽我的研究场地之后，我想知道可能存在什么问题以及如何解决它 舱单：（部分视图） 备份数据库：将数据库复制到SD卡
package com.peter.databasetest;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import com.peter.databasetest.DBAdapter;
public class BackupDB extends AsyncTask<Void, Void, Integer> {
DBAdapter db;
intrc= -10;
intretcode;
intchk;
Stringmessage;
String mypackage;
public Context context;
public static String FOLDER_NAME = "DBfolder";
public static final String DATABASE_NAME = "UserDB.db";
public static final String DATABASE_BACKUP= "UserDB.db";
public static final String BKP_OK = "Backup was SUCCESSFUL.";
public static final String BKP_NOK = "Backup FAILED. ";
@Override
protected void onPreExecute() {
// GET PACKAGE NAME
mypackage = context.getApplicationContext().getPackageName() ;
}
// START BACKUP TO SDCARD
@Override
protected Integer doInBackground(Void... params) {
// DOING BACKUP
Log.i("00000" , "STARTING BACKUP...BACKUP ");
File sd = Environment.getExternalStorageDirectory();
File data = Environment.getDataDirectory();
CREATE A FOLDER /mnt/sdcard<packagename>FOLDER_NAME if it does not exist
File folder = new File(Environment.getExternalStorageDirectory()
+ "/"
+ mypackage
+ "/"
+ FOLDER_NAME);
if(!folder.exists()) {
if (folder.mkdirs()) ;
}
// GET THE PATH OF THE BACKUP ON THE SDCARD
FilefileBackupDir = new File(Environment.getExternalStorageDirectory()
+ "/"
+mypackage
+ "/"
+ FOLDER_NAME
+"/"
+ DATABASE_BACKUP) ;
// IF WE HAVE A BACKUP ON SDCARD, DELETE IT TO MAKE ROOM FOR THE NEW BACKUP
if (fileBackupDir.exists()) {
fileBackupDir.delete();
}else {
* DO NOTHING */
}
// GET CURRENT DB PATH FOR THE COPY
String currentDBPath = "/data/" + mypackage + "/databases/"+ DATABASE_NAME;
// GET CURRENT DB PATH FOR THE BACKUP
String backupDBPath = "/" + mypackage + "/" +FOLDER_NAME + "/" + DATABASE_BACKUP;
FilecurrDB = new File(data, currentDBPath) ;
FilebkpDB = new File(sd, backupDBPath);
FileChannel from = null;
try {
from = new FileInputStream(currDB).getChannel();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
FileChannel to = null;
try {
to = new FileOutputStream(bkpDB).getChannel();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
to.transferFrom(from, 0, from.size());
} catch (IOException e) {
e.printStackTrace();
}
try {
from.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
to.close();
} catch (IOException e) {
e.printStackTrace();
}
retcode = 0;
returnretcode;
// end DoInBackgroung
protectedvoid onPostExecute(Integer retcode, String message) {
if(retcode == 0) {
message = BKP_OK;
SendMessageDialog(message);
}else {
message = BKP_NOK;
SendMessageDialog(message);
}
}
public void SendMessageDialog(String message) {
if (message == BKP_OK ) {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("My Database")
.setMessage(message) // Title of the dialog
.setCancelable(true) // Does allow the use of Back Button on the hardware
.setIcon(R.drawable.ecg)// da picture
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
dialog.cancel();
}
});
final AlertDialog alert = builder.create();
alert.show();
}else {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("My Database")
.setMessage(message) // Title of the dialog
.setCancelable(true) // Does allow the use of Back Button on the hardware
.setIcon(R.drawable.bad)// da picture
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
dialog.cancel();
}
});
final AlertDialog alert = builder.create();
alert.show();
}
}
}
<activity
android:name=".BackupDB"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.peter.databasetest.BACKUPDB" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
问题是在清单文件中，您正在将application:name设置为te BackupDB类，并且该类只是一个异步任务，而不是应用程序 从“安卓：名称”的解释中可以看出： 实现总体功能的类的可选名称
此软件包的android.app.Application。[字符串]
问题是在清单文件中，您正在将application:name设置为te BackupDB类，并且该类只是一个异步任务，而不是应用程序 从“安卓：名称”的解释中可以看出： 实现总体功能的类的可选名称
此软件包的android.app.Application。[字符串]
android:name=“com.peter.databasetest.BackupDB”>这里你是在对android说你的类BackupDP扩展了应用程序，是真的吗？我不知道基于什么他们建议你引用清单文件中的
BackupDBBackupDBBackupDBBackupDb package com.peter.databasetest;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import com.peter.databasetest.DBAdapter;
public class BackupDB extends AsyncTask<Void, Void, Integer> {
DBAdapter db;
intrc= -10;
intretcode;
intchk;
Stringmessage;
String mypackage;
public Context context;
public static String FOLDER_NAME = "DBfolder";
public static final String DATABASE_NAME = "UserDB.db";
public static final String DATABASE_BACKUP= "UserDB.db";
public static final String BKP_OK = "Backup was SUCCESSFUL.";
public static final String BKP_NOK = "Backup FAILED. ";
@Override
protected void onPreExecute() {
// GET PACKAGE NAME
mypackage = context.getApplicationContext().getPackageName() ;
}
// START BACKUP TO SDCARD
@Override
protected Integer doInBackground(Void... params) {
// DOING BACKUP
Log.i("00000" , "STARTING BACKUP...BACKUP ");
File sd = Environment.getExternalStorageDirectory();
File data = Environment.getDataDirectory();
CREATE A FOLDER /mnt/sdcard<packagename>FOLDER_NAME if it does not exist
File folder = new File(Environment.getExternalStorageDirectory()
+ "/"
+ mypackage
+ "/"
+ FOLDER_NAME);
if(!folder.exists()) {
if (folder.mkdirs()) ;
}
// GET THE PATH OF THE BACKUP ON THE SDCARD
FilefileBackupDir = new File(Environment.getExternalStorageDirectory()
+ "/"
+mypackage
+ "/"
+ FOLDER_NAME
+"/"
+ DATABASE_BACKUP) ;
// IF WE HAVE A BACKUP ON SDCARD, DELETE IT TO MAKE ROOM FOR THE NEW BACKUP
if (fileBackupDir.exists()) {
fileBackupDir.delete();
}else {
* DO NOTHING */
}
// GET CURRENT DB PATH FOR THE COPY
String currentDBPath = "/data/" + mypackage + "/databases/"+ DATABASE_NAME;
// GET CURRENT DB PATH FOR THE BACKUP
String backupDBPath = "/" + mypackage + "/" +FOLDER_NAME + "/" + DATABASE_BACKUP;
FilecurrDB = new File(data, currentDBPath) ;
FilebkpDB = new File(sd, backupDBPath);
FileChannel from = null;
try {
from = new FileInputStream(currDB).getChannel();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
FileChannel to = null;
try {
to = new FileOutputStream(bkpDB).getChannel();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
to.transferFrom(from, 0, from.size());
} catch (IOException e) {
e.printStackTrace();
}
try {
from.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
to.close();
} catch (IOException e) {
e.printStackTrace();
}
retcode = 0;
returnretcode;
// end DoInBackgroung
protectedvoid onPostExecute(Integer retcode, String message) {
if(retcode == 0) {
message = BKP_OK;
SendMessageDialog(message);
}else {
message = BKP_NOK;
SendMessageDialog(message);
}
}
public void SendMessageDialog(String message) {
if (message == BKP_OK ) {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("My Database")
.setMessage(message) // Title of the dialog
.setCancelable(true) // Does allow the use of Back Button on the hardware
.setIcon(R.drawable.ecg)// da picture
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
dialog.cancel();
}
});
final AlertDialog alert = builder.create();
alert.show();
}else {
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("My Database")
.setMessage(message) // Title of the dialog
.setCancelable(true) // Does allow the use of Back Button on the hardware
.setIcon(R.drawable.bad)// da picture
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
dialog.cancel();
}
});
final AlertDialog alert = builder.create();
alert.show();
}
}
}
02-12 07:36:06.015: E/AndroidRuntime(987): FATAL EXCEPTION: main
02-12 07:36:06.015: E/AndroidRuntime(987): java.lang.RuntimeException: Unable to instantiate application com.peter.databasetest.BackupDB:
: com.peter.databasetest.BackupDB cannot be cast to android.app.Application
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.LoadedApk.makeApplication(LoadedApk.java:501)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4124)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.ActivityThread.access$1300(ActivityThread.java:130)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1255)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.os.Handler.dispatchMessage(Handler.java:99)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.os.Looper.loop(Looper.java:137)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.ActivityThread.main(ActivityThread.java:4745)
02-12 07:36:06.015: E/AndroidRuntime(987): at java.lang.reflect.Method.invokeNative(Native Method)
02-12 07:36:06.015: E/AndroidRuntime(987): at java.lang.reflect.Method.invoke(Method.java:511)
02-12 07:36:06.015: E/AndroidRuntime(987): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-12 07:36:06.015: E/AndroidRuntime(987): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-12 07:36:06.015: E/AndroidRuntime(987): at dalvik.system.NativeStart.main(Native Method)
02-12 07:36:06.015: E/AndroidRuntime(987): Caused by: java.lang.ClassCastException: com.peter.databasetest.BackupDB cannot be cast to android.app.Application
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.Instrumentation.newApplication(Instrumentation.java:982)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.Instrumentation.newApplication(Instrumentation.java:967)
02-12 07:36:06.015: E/AndroidRuntime(987): at android.app.LoadedApk.makeApplication(LoadedApk.java:496)
02-12 07:36:06.015: E/AndroidRuntime(987): ... 11 more
<activity
android:name=".BackupDB"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.peter.databasetest.BACKUPDB" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
02-12 13:00:16.569: W/dalvikvm(30656): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
02-12 13:00:16.650: E/AndroidRuntime(30656): FATAL EXCEPTION: main
02-12 13:00:16.650: E/AndroidRuntime(30656): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.peter.databasetest/com.peter.databasetest.BackupDB}: java.lang.ClassCastException: com.peter.databasetest.BackupDB cannot be cast to android.app.Activity
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.ActivityThread.access$600(ActivityThread.java:130)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.os.Handler.dispatchMessage(Handler.java:99)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.os.Looper.loop(Looper.java:137)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.ActivityThread.main(ActivityThread.java:4745)
02-12 13:00:16.650: E/AndroidRuntime(30656): at java.lang.reflect.Method.invokeNative(Native Method)
02-12 13:00:16.650: E/AndroidRuntime(30656): at java.lang.reflect.Method.invoke(Method.java:511)
02-12 13:00:16.650: E/AndroidRuntime(30656): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-12 13:00:16.650: E/AndroidRuntime(30656): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-12 13:00:16.650: E/AndroidRuntime(30656): at dalvik.system.NativeStart.main(Native Method)
02-12 13:00:16.650: E/AndroidRuntime(30656): Caused by: java.lang.ClassCastException: com.peter.databasetest.BackupDB cannot be cast to android.app.Activity
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
02-12 13:00:16.650: E/AndroidRuntime(30656): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
02-12 13:00:16.650: E/AndroidRuntime(30656): ... 11 more
>Question:
>Is there any known limitation calling an AsyncTask by way of startActivityForResult?
>Could this be a factor?