NullPointerException异常误差ArrayAdapter和ListView [英] NullPointerException Error for ArrayAdapter and ListView

问题描述

我有通过钥匙hubahuba收到来自编辑的文本在不同的活动用户输入的列表视图。当我点击包含此的.class我收到的基础上，我知道它与我的字符串trackinput行做的logcat的NullPointerException异常错误水龙头请任何帮助球员？

 公共静态的ArrayList＆LT;串GT;名单=新的ArrayList＆LT;串GT;（）;
 公共静态ArrayAdapter＆LT;串GT;适配器;LisstView LV;
串trackinput;@覆盖
保护无效的onCreate（捆绑savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.activity_argue_list）;           // ListView控件code    LV的ListView =（ListView控件）findViewById（android.R.id.list）;            //意图从其他活动接收    意向I = getIntent（）;    串trackinput = i.getExtras（）的getString（hubahuba）;            //基本适配器    适配器=新ArrayAdapter＆LT;串GT;（这一点，android.R.layout.simple_list_item_1，清单）;
    lv.setAdapter（适配器）;
    list.add（0，trackinput）;
    adapter.notifyDataSetChanged（）;
    setListAdapter（适配器）;}
 

这是从活动一去到ListView在活动2：

 公共无效的onClick（视图v）{
 意图I =新意图（这一点，ArgueListActivity.class）;
 i.putExtra（hubahuba，whatedit.getText（）的toString（））;
 whatedit.setText（）;
}
 

解决方案

您不必创建一个新的实例意图

您可以做这样的：

 字符串trackinput = getIntent（）getStringExtra（hubahuba）;
 

另外，作为科林指出

  LisstView LV;
 

和

 的ListView LV =（ListView控件）findViewById（android.R.id.list）;
 

暧昧

---

你投入的意图数据后，你必须启动活动，并把它传递的意图
吧。

 公共无效的onClick（视图v）{
 意图I =新意图（这一点，ArgueListActivity.class）;
 i.putExtra（hubahuba，whatedit.getText（）的toString（））;
 whatedit.setText（）;
 startActivity㈠
}
 

I have a listview that receives user input from edit text in a different activity via key "hubahuba". When I click on the tap that contains this .class I receive the NullPointerException Error based on the logcat I know it has to do with my "String trackinput" Line PLEASE any help guys???

 public static ArrayList<String> list = new ArrayList<String>();
 public static ArrayAdapter<String> adapter;

LisstView lv;
String trackinput;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_argue_list);

           //listViewCode

    ListView lv = (ListView)findViewById(android.R.id.list);

            //Intent to receive from other activity

    Intent i = getIntent();

    String trackinput = i.getExtras().getString("hubahuba");

            //basic adapter

    adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list);
    lv.setAdapter(adapter);
    list.add(0, trackinput);
    adapter.notifyDataSetChanged();
    setListAdapter(adapter);

}

This is from activity 1 going to the listView in Activity 2:

public void onClick(View v) { 
 Intent i = new Intent(this, ArgueListActivity.class); 
 i.putExtra("hubahuba",whatedit.getText().toString()); 
 whatedit.setText("");
}

解决方案

You don't have to create a new instance of Intent

You can just do it like this:

String trackinput = getIntent().getStringExtra("hubahuba");

Also as Collin pointed out

LisstView lv;

and

ListView lv = (ListView)findViewById(android.R.id.list);

are ambiguous

---

After you put data into the intent you have to start the activity, and pass it the intent to it.

public void onClick(View v) { 
 Intent i = new Intent(this, ArgueListActivity.class); 
 i.putExtra("hubahuba",whatedit.getText().toString()); 
 whatedit.setText("");
 startActivity(i)
}

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