我更喜欢组装代码，它会在方法中创建警报并将其包装到单独的类中。
但是，不幸的是，在调用一个事件后，应用程序崩溃了，我认为这是因为该方法中传递的上下文。请告诉我如何正确处理包含在类中的方法中的context参数。
这是一个单独的类中的方法：
public void showAlertDialogWithTwoButtons(Context context, CharSequence title, CharSequence message, final DialogCallback callback) {
this.context=context;
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(context);
// set dialog message
alertDialogBuilder
.setTitle(title.toString())
.setMessage(message.toString())
.setCancelable(false)
.setPositiveButton("Yes",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
if (callback != null) {
callback.onClickYes();
}
dialog.cancel();
}
})
.setNegativeButton("No",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
if (callback != null) {
callback.onClickNo();
}
dialog.cancel();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
这是MainActivity中的方法调用：
if (id == R.id.action_hide) {
alertBuiders.showAlertDialogWithTwoButtons(MainActivity.this, "Wanna hide?", "Do you want to hide?", new DialogCallback() {
@Override
public void onClickYes() {
hideApp();
}
@Override
public void onClickNo() {
return;
}
});
}
如何在MainActivity中调用它？
以下是错误日志：
10-25 12:19:59.361 4929-4929/com.example.fedotarte.myfirstapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.fedotarte.myfirstapplication, PID: 4929
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.fedotarte.myfirstapplication.AlertBuiders.showAlertDialogWithTwoButtons(android.content.Context, java.lang.CharSequence, java.lang.CharSequence, com.example.fedotarte.myfirstapplication.DialogCallback)' on a null object reference
at com.example.fedotarte.myfirstapplication.MainActivity.onOptionsItemSelected(MainActivity.java:79)
at android.app.Activity.onMenuItemSelected(Activity.java:3435)
at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:360)
at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:194)
at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:110)
at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:110)
at android.support.v7.app.ToolbarActionBar$2.onMenuItemClick(ToolbarActionBar.java:69)
at android.support.v7.widget.Toolbar$1.onMenuItemClick(Toolbar.java:204)
at android.support.v7.widget.ActionMenuView$MenuBuilderCallback.onMenuItemSelected(ActionMenuView.java:776)
at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:821)
at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:158)
at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:968)
at android.support.v7.view.menu.MenuPopup.onItemClick(MenuPopup.java:127)
at android.widget.AdapterView.performItemClick(AdapterView.java:318)
at android.widget.AbsListView.performItemClick(AbsListView.java:1165)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3134)
at android.widget.AbsListView$3.run(AbsListView.java:4049)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
答案 0 :(得分：1)
试试这个
// create alert dialog is wrong way remove this code
AlertDialog alertDialog = alertDialogBuilder.create();
//写方式是创建一个对话框 AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder（context）.create（）;