Question

这是我的java代码;

public class Main extends Activity {

ListView lvLokacije;
String sLista, class;
Class<?> ourClass;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    lvLokacije = (ListView) findViewById(R.id.lvLokacije);

    String lista[] = { "Class1", "Class2", "Class3", "EXIT", };

    ArrayAdapter<String> aLista = new ArrayAdapter<String>(Main.this,
                 R.layout.costum_list_item2, lista);
        lvLokacije.setAdapter(aLista);

         lvLokacije.setOnItemClickListener(new OnItemClickListener() {
             public void onItemClick(AdapterView<?> myAdapter, View myView,
                     int myItemInt, long mylng) {

                sLista = (String) (lvLokacije.getItemAtPosition(myItemInt));
                String ispis = sLista.toString();

                if (ispis.contentEquals("Class1")) {
                    class= "myClass1";
                } else if (ispis.contentEquals("Class2")) {
                    class= "myClass2";
                } else if (ispis.contentEquals("Class3")) {
                    class= "myClass3";
                }  else if (ispis.contentEquals("IZLAZ")) {
                    onBackPressed();
                }

                try {
                    ourClass = Class.forName("crni03.obracun." + class);
                } catch (ClassNotFoundException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                Intent ourIntent = new Intent(Main.this, ourClass);

                startActivity(ourIntent);

            }
        });     
}
@Override
public void onBackPressed() {

    android.os.Process.killProcess(android.os.Process.myPid());
    // This above line close correctly
}

}

这是costum_list_item2 XML;

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    style="?android:attr/spinnerItemStyle"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ellipsize="marquee"
    android:padding="3dp"
    android:singleLine="true"
    android:textColor="#FFFF4D"
    android:textSize="19sp" />

我在costum_list_item2中设置了文本颜色，但我想从java更改它，但我不知道如何。我想要一个用户可以更改列表项颜色的功能。

当我将android:id="@android:id/text1"更改为android:id="@+id/text1"时我可以创建一个TextView并调用该id，但这是我可以去的。每当我尝试使用TextViev做某事时，我都会收到null.pointer.exeption错误。

感谢名单！

Answer 1

您无法在此处直接访问textview。由于每个textview都是id为＃lvLokacije＆＃39;的视图中的子元素。什么是lvLokacije在这里。如果它是listview或gridview，那么您可以使用getView（）方法访问视图的行。这就是我使用它的方法，其中position是listview中元素的从零开始的索引。

ListView listView;
String list[] = { "TEXT", "TEXT2", "TEXT3", "TEXT4"};

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    listView = (ListView) findViewById(R.id.listView);
    ListAdapter adapter = new ListCellAdapter(this);
    listView.setAdapter(adapter);
}


public class ListCellAdapter extends BaseAdapter
{
    Context ctx;
    TextView txtView;
    public ListCellAdapter(Context context)
    {
        super();
        ctx = context;
    }

    @Override
    public int getCount() {
        return list.length;
    }

    @Override
    public Object getItem(int arg0) {
        return null;
    }

    @Override
    public long getItemId(int arg0) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) 
    {
        View row = convertView;
        if (row == null)
        {
            LayoutInflater inflater = (LayoutInflater) ctx
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.costum_list_item2, parent, false);
        }
        txtView = ((TextView)(row.findViewById(android.R.id.text1)));
        txtView.setText(String.valueOf(position));
        if(position == 1)
        {
            txtView.setTextColor(Color.CYAN);
        }
        else
        {
            txtView.setTextColor(Color.BLUE);
        }
        return row;
    }
}

}

Answer 2

Thanx Durga !!! 在Durga帮助之后，这是我的代码

public class Main extends Activity {

ListView lvLokacije;
String class;
Class<?> ourClass;

 String list[] = { "Class1", "Class2", "Class3",
         "EXIT", };

 protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);      
     lvLokacije = (ListView) findViewById(R.id.lvLokacije);
     ListAdapter adapter = new ListCellAdapter(this);
    lvLokacije.setAdapter(adapter);

 }

 public class ListCellAdapter extends BaseAdapter implements
         OnItemClickListener {
     Context ctx;
     TextView txtView;

     public ListCellAdapter(Context context) {
         super();
         ctx = context;
         lvLokacije.setOnItemClickListener(this);
     }

    public int getCount() {
        return list.length;
    }

     public Object getItem(int arg0) {
         return null;
     }

     public long getItemId(int arg0) {
         return 0;
     }

    public View getView(int position, View convertView, ViewGroup parent) {
         View row = convertView;
         if (row == null) {
             LayoutInflater inflater = (LayoutInflater) ctx
                     .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.costum_list_item2, parent,
                    false);
         }
        txtView = ((TextView) (row.findViewById(android.R.id.text1)));
        txtView.setText(String.valueOf(list[position]));

         txtView.setTextColor(Color.BLUE);

         return row;
    }

     public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
            long arg3) {
        // TODO Auto-generated method stub

            Object oList = (list[arg2]);
            String ispis = sList.toString();
            if (ispis.contentEquals("Class1")) {
                class = "myClass1";
            } else if (ispis.contentEquals("Class2")) {
                class = "myClass2";
            } else if (ispis.contentEquals("Class3")) {
                class = "myClass3";
            }  else if (ispis.contentEquals("EXIT")) {
                onBackPressed();                
            }
            try {
                ourClass = Class.forName("crni03.obracun." + class);
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            Intent ourIntent = new Intent(Main.this, ourClass);

            startActivity(ourIntent);


    }
}

@Override
public void onBackPressed() {

    android.os.Process.killProcess(android.os.Process.myPid());
    // This above line close correctly
}

@Override
protected void onResume() {
    // TODO Auto-generated method stub
    super.onResume();
}

@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
}

}

从java更改数组适配器的文本颜色

2 个答案: