java自动完成支持片段。setPlaceFields在应用程序启动时崩溃

Question

首先，我想说的是，我是这个“编程世界”的新手，但我一直在与google Places的autocompleteFragment抗争， 我试图在我的应用程序中实现autocompleteFragment，但在进入我的“欢迎活动”后，它抛出一个错误并压碎应用程序：

    Process: com.app.mk.transport, PID: 20295
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.mk.transport/com.app.mk.transport.Welcome}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.安卓.libraries.places.widget.AutocompleteSupportFragment.setPlaceFields(java.util.List)' on a null object reference
        at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
        at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
        at 安卓.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at 安卓.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at 安卓.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
        at 安卓.os.Handler.dispatchMessage(Handler.java:106)
        at 安卓.os.Looper.loop(Looper.java:193)
        at 安卓.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.安卓.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.安卓.libraries.places.widget.AutocompleteSupportFragment.setPlaceFields(java.util.List)' on a null object reference
        at com.app.mk.transport.Welcome.setUpLocationPicker(Welcome.java:237)
        at com.app.mk.transport.Welcome.onCreate(Welcome.java:216)
        at 安卓.app.Activity.performCreate(Activity.java:7136)
        at 安卓.app.Activity.performCreate(Activity.java:7127)
        at 安卓.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
        at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
        at 安卓.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at 安卓.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at 安卓.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
        at 安卓.os.Handler.dispatchMessage(Handler.java:106) 
        at 安卓.os.Looper.loop(Looper.java:193) 
        at 安卓.app.ActivityThread.main(ActivityThread.java:6669) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.安卓.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:858) 

这是我的代码：

        if (!Places.isInitialized()) {
            Places.initialize(getApplicationContext(), String.valueOf(R.string.google_api_key));
        }
            autocompleteFragment.setPlaceFields(Arrays.asList(Place.Field.ADDRESS));


        autocompleteFragment.setOnPlaceSelectedListener(new PlaceSelectionListener() {

            @Override
            public void onPlaceSelected(Place place) {

                if (location_switch.isChecked()) {
                    destination = place.getAddress();
                    destination = destination.replace(" ", "+");
                    getDirection();
                }
            }

            @Override
            public void onError(Status status) {
                // TODO: Handle the error.
                Toast.makeText(Welcome.this, "" + status.toString(), Toast.LENGTH_SHORT).show();
                Log.i(TAG, "An error occurred: " + status);
            }
        });

我不确定我做错了什么，但如果有人能指出我的错误，我会非常感激

如果我需要给你看其他的“代码”或任何东西，只要告诉我我是否遗漏了它

谢谢