Question

这是我从数据库中读取数据的代码。在这里，我只是接收值并使用“Toast”类打印它们。

public void onClickLogin(View btnLogin)
{
    String email,password;
    String[] cols = new String[] {DataBase_Server.EMAIL, DataBase_Server.PASS};
    EditText edtPassword = (EditText) findViewById(R.id.edtPassword);
    EditText edtLoginId = (EditText) findViewById(R.id.btnLogin);
    DataBase_Server database=new DataBase_Server(login.this);
    SQLiteDatabase db=database.getReadableDatabase();
    Cursor c=db.query(DataBase_Server.TABLE, null, null, null, null, null, null);
    //startManagingCursor(c);
    c.moveToFirst();
    email=c.getString(c.getColumnIndex(DataBase_Server.EMAIL));
    password=c.getString(c.getColumnIndex(DataBase_Server.PASS));
    Toast.makeText(this,email+" hello "+password, Toast.LENGTH_SHORT).show();
}

代码中没有语法错误但是当我运行我的应用程序并单击我的登录按钮时，我得到一个强制关闭对话框，最终退出我的应用程序，在“logcat”中我看到一些异常，如“Unable”打开堆栈文件......访问被拒绝“等等。

logcat的：

09-20 01:28:55.524: E/AndroidRuntime(378): java.lang.IllegalStateException: Could not execute method of the activity
09-20 01:28:55.524: E/AndroidRuntime(378):  at android.view.View$1.onClick(View.java:2031)
09-20 01:28:55.524: E/AndroidRuntime(378):  at android.view.View.performClick(View.java:2364)
09-20 01:28:55.564: E/dalvikvm(378): Unable to open stack trace file '/data/anr/traces.txt': Permission denied
09-20 01:45:58.265: E/AndroidRuntime(408): Uncaught handler: thread main exiting due to uncaught exception
09-20 01:45:58.295: E/AndroidRuntime(408): java.lang.IllegalStateException: Could not execute method of the activity
09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.View$1.onClick(View.java:2031)
09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.View.performClick(View.java:2364)
09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.View.onTouchEvent(View.java:4179)
09-20 01:45:58.295: E/AndroidRuntime(408):  at android.widget.TextView.onTouchEvent(TextView.java:6541)
09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.View.dispatchTouchEvent(View.java:3709)
09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
  09-20 01:45:58.295: E/AndroidRuntime(408):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
    09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
     09-20 01:45:58.295: E/AndroidRuntime(408):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
      09-20 01:45:58.295: E/AndroidRuntime(408):    at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
    09-20 01:45:58.295: E/AndroidRuntime(408):  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
     09-20 01:45:58.295: E/AndroidRuntime(408):     at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
      09-20 01:45:58.295: E/AndroidRuntime(408):    at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
    09-20 01:45:58.295: E/AndroidRuntime(408):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
     09-20 01:45:58.295: E/AndroidRuntime(408):     at android.os.Handler.dispatchMessage(Handler.java:99)
    09-20 01:45:58.295: E/AndroidRuntime(408):  at android.os.Looper.loop(Looper.java:123)
    09-20 01:45:58.295: E/AndroidRuntime(408):  at android.app.ActivityThread.main(ActivityThread.java:4363)
   09-20 01:45:58.295: E/AndroidRuntime(408):   at java.lang.reflect.Method.invokeNative(Native Method)
    09-20 01:45:58.295: E/AndroidRuntime(408):  at java.lang.reflect.Method.invoke(Method.java:521)
  09-20 01:45:58.295: E/AndroidRuntime(408):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
  09-20 01:45:58.295: E/AndroidRuntime(408):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
   09-20 01:45:58.295: E/AndroidRuntime(408):   at  dalvik.system.NativeStart.main(Native Method)
     09-20 01:45:58.295: E/AndroidRuntime(408): Caused by: java.lang.reflect.InvocationTargetException
  09-20 01:45:58.295: E/AndroidRuntime(408):    at com.example.curbrain.login.onClickLogin(login.java:36)
   09-20 01:45:58.295: E/AndroidRuntime(408):   at java.lang.reflect.Method.invokeNative(Native Method)
  09-20 01:45:58.295: E/AndroidRuntime(408):    at java.lang.reflect.Method.invoke(Method.java:521)
   09-20 01:45:58.295: E/AndroidRuntime(408):   at android.view.View$1.onClick(View.java:2026)
     09-20 01:45:58.295: E/AndroidRuntime(408):     ... 21 more
   09-20 01:45:58.295: E/AndroidRuntime(408): Caused by: java.lang.ClassCastException: android.widget.Button
   09-20 01:45:58.295: E/AndroidRuntime(408):   ... 25 more
    09-20 01:45:58.325: E/dalvikvm(408): Unable to open stack trace file '/data/anr/traces.txt': Permission denied

XML CODE：

android:onClick="onClickLogin"

Answer 1

您尝试引用XML登录EditText，但实际上您已经使用了Button的ID：

 EditText edtLoginId = (EditText) findViewById(R.id.btnLogin);

因此，您无法将返回的视图（按钮）强制转换为EditText

该ID用于按钮：R.id.btnLogin检查您的XML是否有正确的ID。

在LogCat中解释它的行是：

 09-20 01:45:58.295: E/AndroidRuntime(408): Caused by: java.lang.ClassCastException: android.widget.Button

Answer 2

你有一个错字。以下之间存在大写差异：

android:onClick="onClickLogin"

和

public void OnClickLogin(View btnLogin)

将您的方法更改为小写＆＃34; o＆＃34;：

public void onClickLogin(View btnLogin)

我看到你更新了问题来解决这个错误，但你检查过它是否在你的代码中？

从android数据库中检索数据

2 个答案: