问题
I have developed one application which has 15 screens. Now I want to display custom toast message in all those 15 screens. To do so, I have inflated one layout. But it's working only on one screen. So, I wrote a single method to display custom Toast on all screens. Whenever I want to display toast message, I would just call that method. But i got java.lang.NullPointerException. How to resolve this? The following is my code,
public static void showToastMessage(String message){
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
View layout = inflater.inflate(R.layout.custom_toast,
(ViewGroup) ((Activity) context).findViewById(R.id.customToast));
// set a message
TextView text = (TextView) layout.findViewById(R.id.text);
text.setText(message);
// Toast...
Toast toast = new Toast(context);
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();
}
Log is
java.lang.NullPointerException
at com.guayama.utilities.CommonMethods.showToastMessage(CommonMethods.java:474)
at android.view.View.performClick(View.java:3511)
at android.view.View$PerformClick.run(View.java:14105)
at android.os.Handler.handleCallback(Handler.java:605)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4424)
at java.lang.reflect.Method.invokeNative(Native Method)
回答1:
change your method
from
showToastMessage(String message)
to
showToastMessage(Context context,String message);
it seems context problem to me
your function will look like this
public static void showToastMessage(Context context,String message){
LayoutInflater inflater = context.getLayoutInflater();
View layout = inflater.inflate(R.layout.custom_toast,
(ViewGroup) ((Activity) context).findViewById(R.id.customToast));
// set a message
TextView text = (TextView) layout.findViewById(R.id.text);
text.setText(message);
// Toast...
Toast toast = new Toast(context);
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();
}
回答2:
A custom class implementation of Toast that can be used in any project.
public class ToastMessage {
private Context context;
private static ToastMessage instance;
/**
* @para
m context
*/
private ToastMessage(Context context) {
this.context = context;
}
/**
* @param context
* @return
*/
public synchronized static ToastMessage getInstance(Context context) {
if (instance == null) {
instance = new ToastMessage(context);
}
return instance;
}
/**
* @param message
*/
public void showLongMessage(String message) {
Toast.makeText(context, message, Toast.LENGTH_SHORT).show();
}
/**
* @param message
*/
public void showSmallMessage(String message) {
Toast.makeText(context, message, Toast.LENGTH_LONG).show();
}
/**
* The Toast displayed via this method will display it for short period of time
*
* @param message
*/
public void showLongCustomToast(String message) {
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
View layout = inflater.inflate(R.layout.layout_custom_toast, (ViewGroup) ((Activity) context).findViewById(R.id.ll_toast));
TextView msgTv = (TextView) layout.findViewById(R.id.tv_msg);
msgTv.setText(message);
Toast toast = new Toast(context);
toast.setGravity(Gravity.FILL_HORIZONTAL | Gravity.BOTTOM, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();
}
/**
* The toast displayed by this class will display it for long period of time
*
* @param message
*/
public void showSmallCustomToast(String message) {
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
View layout = inflater.inflate(R.layout.layout_custom_toast, (ViewGroup) ((Activity) context).findViewById(R.id.ll_toast));
TextView msgTv = (TextView) layout.findViewById(R.id.tv_msg);
msgTv.setText(message);
Toast toast = new Toast(context);
toast.setGravity(Gravity.FILL_HORIZONTAL | Gravity.BOTTOM, 0, 0);
toast.setDuration(Toast.LENGTH_SHORT);
toast.setView(layout);
toast.show();
}
}
回答3:
pass Context in and use it as showToastMessage(String message,Context context)
thus:
public static void showToastMessage(String message){
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
View layout = inflater.inflate(R.layout.custom_toast,
(ViewGroup) ((Activity) context).findViewById(R.id.customToast));
// set a message
TextView text = (TextView) layout.findViewById(R.id.text);
text.setText(message);
// Toast...
Toast toast = new Toast(context);
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();
}
回答4:
I think this is the problem,
(Activity) context
You have not passed the context object to this method and you are trying to refer some Context Object which you could have declared globally.
So at this point if your Context Object is null you will get NullPointer. Try to pass the conetxt of your Current Activity in the parameter of your showToastMessage()
回答5:
I have worked on custom toast so please follow the below process and you will use the common method for multiple time.
My custom_toast.xml is:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/custom_toast_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@color/white">
<android.support.v7.widget.CardView
android:id="@+id/card_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
card_view:cardBackgroundColor="@color/grey"
card_view:cardCornerRadius="6dp"
card_view:cardElevation="6dp"
card_view:contentPadding="25dp"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center">
<ImageView
android:id="@+id/custom_toast_image"
android:layout_width="30dp"
android:layout_height="30dp"
android:gravity="center_vertical"
android:src="@drawable/ic_launcher"/>
<TextView
android:id="@+id/custom_toast_message"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:textSize="16dp"/>
</LinearLayout>
</android.support.v7.widget.CardView>
</LinearLayout>
Second thing create one java class: like CustomToast.java
public class CustomToast {
Context context;
public static void showToastMessage(Context context,String message){
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
View layout = inflater.inflate(R.layout.customtoast,
(ViewGroup) ((Activity) context).findViewById(R.id.custom_toast_layout));
// set a message
TextView text = (TextView) layout.findViewById(R.id.custom_toast_message);
text.setText(message);
// Toast...
Toast toast = new Toast(context);
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();
}
}
Third step create the object of CustomToast.java class in your activity and call the method by passing context and message.
CustomToast customToast=new CustomToast();
customToast.showToastMessage(ctx,message);
来源：https://stackoverflow.com/questions/11339980/custom-toast-message-in-all-screens