我怎样才能通过位置得到的ListView视图，设置文本的项目？ [英] How can I get view from ListView by position and set text to item?

问题描述

我想实现自定义列表。还有一个TextView每一行，我想设置文本从的onCreate TextView的那些在下面的方法，但是我得到空指针异常。

I am trying to implement custom list. there is a Textview in each row, I want to set text to those TextView from onCreate in the following way But I get NullPointer exception.

我的自定义列表

public class CustomList extends ArrayAdapter<String>{

private final Activity context;
private final String[] web;
private final Integer[] imageId;


TextView txtTitle;

public CustomList(Activity context, String[] web, Integer[] imageId) {
super(context, R.layout.list_single, web);
this.context = context;
this.web = web;
this.imageId = imageId;
}


@Override
public View getView(int position, View view, ViewGroup parent) {

LayoutInflater inflater = context.getLayoutInflater();
View rowView= inflater.inflate(R.layout.list_single, null, true);
ImageView imageView = (ImageView) rowView.findViewById(R.id.img);

txtTitle = (TextView) rowView.findViewById(R.id.txt);

txtTitle.setText(web[position]);
txtTitle.setText("Menjar Ali");


imageView.setImageResource(imageId[position]);
return rowView;
}




}

我的主要活动：

public class MainActivity extends Activity {

ListView list;

  String[] web = {
    "Google Plus",
      "Twitter",
      "Windows"

  } ;

  Integer[] imageId = {
      R.drawable.ic_launcher,
      R.drawable.ic_launcher,
      R.drawable.ic_launcher

  };
TextView myTextView;

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

    CustomList adapter = new CustomList(MainActivity.this, web, imageId);

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

    list.setAdapter(adapter);


    View vv = list.getChildAt(0);

    TextView tt = (TextView)vv.findViewById(R.id.txt);
    tt.setText("momomo");                        //Here I get the error
}

我list_single.xml

My list_single.xml

<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TableRow>
    <ImageView
        android:id="@+id/img"
        android:layout_width="50dp"
        android:layout_height="50dp"/>
    <TextView
        android:id="@+id/txt"
        android:layout_width="wrap_content"
        android:layout_height="50dp" />
</TableRow>
</TableLayout>

其实，我试图实现与一个EditText，而不是内部滚动型中的EditText单行的ListView让我有滚动倾倒的装备更好的办法，并在这样做，面对各种各样的问题。

Actually, I am trying to implement a single row ListView with an EditText instead of a EditText inside scrollView so that I have better way of scrolling funtionality, and facing various problem in doing that.

所以，如果我有哪里的EditText（里面的ListView）可以从任何地方在Main_activity访问和有效地执行operatiopn像setTet，gettext的，颜色变化等一个precise例子，这将是非常有益的。

So if I have a precise example where the EditText(inside ListView) can be accessed from anywhere in Main_activity and efficiently perform operatiopn like setTet, getText, color change etc, it would be very helpful.

推荐答案

如果你想改变颜色和价值实现 OnItemClick 的ListView 这里 VV 为null，因为你是路过该位置是错误的。

If you want to change color and value implement OnItemClick of ListView here vv is null because the position you are passing that is wrong.

在你的自定义适配器注释掉该行 txtTitle.setText（Menjar阿里）; ，因为在此之前，您指定给网​​络阵列一个值，你又该值设置为 Menjar阿里。因此，它会显示 Menjar阿里的每一行项目。

In your custom adapter comment out this line txtTitle.setText("Menjar Ali"); because before that you assigned a value from web array and again you set that value to Menjar Ali. So, it will show Menjar Ali for every row item.

code段

活动

public class MainActivity extends Activity {

ListView list;

  String[] web = {
    "Google Plus",
      "Twitter",
      "Windows"

  } ;

  Integer[] imageId = {
      R.drawable.ic_launcher,
      R.drawable.ic_launcher,
      R.drawable.ic_launcher

  };
TextView myTextView;

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

    CustomList adapter = new CustomList(MainActivity.this, web, imageId);

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

    list.setAdapter(adapter);
}

list_single.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:gravity="center_vertical" >

    <ImageView
        android:id="@+id/img"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:adjustViewBounds="true"
        android:cropToPadding="false"
        android:scaleType="fitXY"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:id="@+id/txt"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:layout_marginLeft="12dp"
        android:text="text" />

</LinearLayout>

适配器

public class CustomList extends ArrayAdapter<String>{

private final Activity context;
private final String[] web;
private final Integer[] imageId;


TextView txtTitle;

public CustomList(Activity context, String[] web, Integer[] imageId) {
super(context, R.layout.list_single, web);
this.context = context;
this.web = web;
this.imageId = imageId;
}


@Override
public View getView(int position, View view, ViewGroup parent) {
ViewHolder viewHolder;
if(view == null) {
  LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
  view = inflater.inflate(R.layout.list_single, parent, false);
  viewHolder = new ViewHolder();
  viewHolder.imageView = (ImageView) view.findViewById(R.id.img);
  viewHolder.txtTitle = (TextView) view.findViewById(R.id.txt);
  view.setTag(viewHolder);
} else {
  viewHolder = (ViewHolder) view.getTag();
}

viewHolder.txtTitle.setText(web[position]);
viewHolder.imageView.setImageResource(imageId[position]);
return view;
}

private class ViewHolder {
 TextView txtTitle;
 ImageView imageView;
}
}

如果你想改变文字颜色你可以在任何click事件改变它即单击该的TextView 或 OnItemClick 的是的ListView 。

If you want to change textColor you can change it in any click event i.e click on that TextView or OnItemClick of that ListView.

在不断变化的数据的情况下，你必须修改网络数组中的值

In case of changing data you have to modify those values inside web array

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