// 一般做法
public void showToast(Context context, String msg) {  Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
} 

// 如果Activity或Fragment有继承基类，则在基类中变成
public void showToast(String msg) {  Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
}
或
public void showToast(String msg) {  Toast.makeText(getActivity(), msg, Toast.LENGTH_SHORT).show();
} 

// 如果有自定Application的话，譬如：
public class MyApplication extends Application {  private static Context mContext;  @Override  public void onCreate() {  super.onCreate();  mContext = getApplicationContext();  }  public static Context getContext() {  return mContext;  }
}
// 则可以自定义ToastUtil类
class ToastUtil{public static void show(String msg) {  Toast.makeText(MyApplication.getContext(), msg, Toast.LENGTH_SHORT).show(); }
}

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" >  //可以根据实际情况来自定义Toast的显示样式  <solid android:color="#ff5252" />  <corners android:radius="5dp" />  <padding  android:bottom="10dp"  android:left="15dp"  android:right="15dp"  android:top="10dp" />
</shape> 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:background="@drawable/toast_custom_bg"  android:orientation="vertical" >  <TextView  android:id="@+id/tv_toast"  android:layout_width="wrap_content"  android:layout_height="wrap_content"  android:textColor="@color/white"  android:textSize="16sp" />  </LinearLayout>

class ToastUtil{public static void show(String msg) {  LinearLayout v = (LinearLayout) LinearLayout.inflate(MyApplication.getContext(), R.layout.toast_custom, null);  TextView tv_toast = (TextView) v.findViewById(R.id.tv_toast);  tv_toast.setText(msg);  Toast toast = new Toast(MyApplication.getContext());  toast.setGravity(Gravity.CENTER, 0, 0);//可以自定义Toast显示在屏幕上的位置
        toast.setDuration(Toast.LENGTH_SHORT);  toast.setView(v);  toast.show();  }
}