在android中更改数组中的值

Question

当我单击Governates_nameedt（EditText）时，我有两个想要的数组。在AlertDialog中显示Governate_names，并根据我选择的值，在state_names数组中选择值。当我运行代码时，asList被更改，我在＜code＞create（）中得到一个错误。show（） 处于状态_nameedt（编辑文本）。

我的代码

  Governorates_names = Arrays.asList("Ad Dakhiliyah"
                ,"Ad Dhahirah"
                ,"Al Batinah North"
                ,"Al Batinah South"
                ,"Al Buraimi"
                ,"Al Wusta"
                ,"Ash Sharqiyah North"
                ,"Ash Sharqiyah South"
                ,"Dhofar"
                ,"Muscat"
                ,"Musandam");
        if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Ad Dakhiliyah"))
            state_names = Arrays.asList("Nizwa","Samail","Bahla","Al Hamra","Manah","Izki","Adam"  );

        else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Ad Dhahirah"))
            state_names = Arrays.asList("Ibri","Yanqul","Dhank");

        else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Al Batinah North")){
            state_names = Arrays.asList("Sohar","Shinas","Liwa","Saham","Al Khaburah","Suwayq");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Al Batinah South")){
            state_names = Arrays.asList("Nakhal","Wadi Al Maawil","Al Musanaah","Barka","Rustaq");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Al Buraimi")){
            state_names = Arrays.asList("Al Buraimi","Mahdah","Al Sinas");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Al Wusta")){
            state_names = Arrays.asList("Haima","Duqm","Mahout","Al Jazur");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Ash Sharqiyah North")){
            state_names = Arrays.asList("Ibra","Al-Mudhaibi","Bidiyah","Wadi Bani Khaled","Dema Wa Thaieen","Al Qabil");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Ash Sharqiyah South")){
            state_names = Arrays.asList("Masirah","Sur","Jalan Bani Bu Hassan","Jalan Bani Bu Ali","Al Kamil Wal Wafi");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Dhofar")){
            state_names = Arrays.asList("Salalah","Taqah","Mirbat","Thumrait","Sadah","Rakhyut","Dhalkut","Muqshin","Shalim and the Hallaniyat Islands","Al-Mazyona");

        }else if(String.valueOf(Governorates_nameedt.getText().toString()).equals("Dhofar")){
            state_names = Arrays.asList("Muttrah","Bawshar","Seeb","Al Amarat","Qurayyat");

        }else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Musandam")){
            state_names = Arrays.asList("Khasab","Bukha","Daba Al Bayah","Madha");


        }

        final ArrayAdapter<String> Governorates_name_Opt = new ArrayAdapter<>(personal_info.this, android.R.layout.simple_spinner_dropdown_item, Governorates_names);
        final List<String> finalOpt1 = Governorates_names;
        Governorates_nameedt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new AlertDialog.Builder(personal_info.this)
                        .setTitle("Select ")
                        .setAdapter(Governorates_name_Opt, new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int which) {
                                Governorates_nameedt.setText(finalOpt1.get(which).toString());
                                dialog.dismiss();
                            }
                        }).create().show();
            }
        });
        final ArrayAdapter<String> state_name_Opt = new ArrayAdapter<>(personal_info.this, android.R.layout.simple_spinner_dropdown_item, state_names);
        final List<String> finalOpt2 = state_names;
        state_nameedt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new AlertDialog.Builder(personal_info.this)
                        .setTitle("Select ")
                        .setAdapter(state_name_Opt, new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int which) {
                                state_nameedt.setText(finalOpt2.get(which).toString());
                                dialog.dismiss();
                            }
                        }).create().show();
            }
        });

我的错误

05-13 16:42:25.7208190-8190/com.example.hamdaalissaei。final_flah W/dalvikvm:threadid=1：线程退出时出现未捕获异常（组=0xa61a1908）05-13 16:42:25.724 8190-8190/com.example.hamdaalissaei。final_flah E/AndroidRuntime：致命异常：android.support.v7.app.AlertController.setupView（AlertController.java:538）的android.support.v7.app.AlertController.setupView（AlertController.java:226）上的android.widget.ArrayAdapter.getCount（ArrayDapter.java:330）上的main java.lang.NullPointerExceptionandroid.support.v7.app.AlertDialog.onCreate（AlertDialog.java:257）在android.app.Dialog.dispatchOnCreate（Dialog.java:355）在android.app.Dialog.show（Dialog.java:260）在com.example.hamdaalissaei.final_flah.personal_info$6.onClick（personal.info.java:247）在android.view.view.view.performClick（view.java:4204）在andro.os.handleCallback运行（view.java:17355）android.os.Handler.dispatchMessage（Handler.java:725）在android.os.Looper.loop（Looper.java:137）在android.app.ActivityThread.main（ActivityThread.java:5041）在java.lang.reflect.Method。java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（zygoTenit.java:793）在com.android.internal.os.zyoteinit.main（zyotenit.java:560）在dalvik.system.NativeStart。main（本地方法）05-13 16:42:25.724 466-835/system_process W/ActivityManager:Force finishing activity com.example.hamdaalissaei.final_flah/.personal_info

请帮我解决这个问题

Answer 1

从堆栈跟踪中:

8190/com.example.hamdaalissaei.final_flah E/AndroidRuntime: FATAL EXCEPTION: main java.lang.NullPointerException at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330) at 

您作为输入放置的数组之一似乎为 null。从你的代码来看，state_names似乎是问题所在。也许没有一个if else语句实际上有效。尝试将

else if( String.valueOf(Governorates_nameedt.getText().toString()).equals("Musandam")){
        state_names = Arrays.asList("Khasab","Bukha","Daba Al Bayah","Madha");
    } else {
        state_names = new List<String>();
}

由于ArrayAdapter所做的是尝试从您输入的数组中找出数组的大小，因此state_names似乎为空。

编辑：state_names似乎取决于EditTextGovernorates_nameedt的值。EditText不是一件神奇的事情，每次编辑它时，它都会调用您创建的（如果有的话）循环。为此，添加一个TextWatcher：

Governorates_nameedt.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

        }

        @Override
        public void afterTextChanged(Editable s) {
            //Put your if else loop HERE
        }
    });

当您在用户输入任何内容之前首次运行代码时，只需启动对新列表state_names