空指针上LayoutInflater - Android电子 [英] NullPointer on LayoutInflater - Android

问题描述

我在我打电话，我MainActivity另一个Java文件中的类。我需要一些充气布局在外部类中。我遇到的问题是指定的范围内，因为当我试着吹大的布局，我得到一个空指针异常。本类不具有它自己的的onCreate（）的方法，所以我需要从我的MainActivity通过上下文？不知道如何去做。这是导致我的 NullPointerException异常：

 上下文的背景下= getApplicationContext（）;
LayoutInflater吹气=（LayoutInflater）context.getApplicationContext（）。getSystemService（Context.LAYOUT_INFLATER_SERVICE）;;
 

NullPointerException异常在上下文背景：

 公共类CameraListener扩展活动实现OnCameraChangeListener {    私有静态最终诠释SCALE_HEIGHT = 50;
    GoogleMap的MMAP;
    GoogleC3iActivity mParent;
    上下文的背景下= getApplicationContext（）;
 

解决方案

多重问题

第一

 上下文的背景下= getApplicationContext（）;
LayoutInflater吹气=（LayoutInflater）context.getSystemService（Context.LAYOUT_INFLATER_SERVICE）;
 

您不应该需要getApplicationContext（），因为你已经拥有它。

或（学分：@Delyan）的

  LayoutInflater.from（上下文）
 

二

上下文的背景下= getApplicationContext（）; 在的setContentView 不起作用。所以，你需要你打电话后，初始化背景的setContentView 在的onCreate

  @覆盖
公共无效的onCreate（捆绑savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.home）;
    上下文= getApplicationContext（）;
 

也是一样的 LayoutInflater ，你需要初始化它的的onCreate

I have a class in another java file that I'm calling in my MainActivity. I need to inflate some layouts in the external class. The problem I'm having is specifying the context, because when I try to inflate the layouts I get a Null Pointer Exception. The class doesn't have it's own onCreate() method so I need to pass the context from my MainActivity? Not sure how to go about it. This is causing me the NullPointerException:

Context context = getApplicationContext();
LayoutInflater inflater = (LayoutInflater)context.getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);;

NullPointerException on Context context:

public class CameraListener extends Activity implements OnCameraChangeListener {

    private static final int SCALE_HEIGHT = 50;
    GoogleMap mMap;
    GoogleC3iActivity mParent;


    Context context = getApplicationContext();

解决方案

Multiple Issues

First

Context context = getApplicationContext();
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

You shouldn't need the getApplicationContext(), since you already have it.

OR (credits : @Delyan)

LayoutInflater.from(context) 

Second

Context context = getApplicationContext(); does not work before setContentView. So you need to initialize context after you call setContentView in your onCreate

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.home);
    context = getApplicationContext() ;

Same goes for LayoutInflater, you need to initialize it in the onCreate

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