Question

我是Android的新手，这是我的问题，我有一个弹出的对话框，假设使用android Http post将表单提交到URL，当我单击表单的提交按钮时，它强制关闭应用程序，我从logcat收到一条错误消息，说它是一个空指针。

protected Dialog onCreateDialog(int id) {
    switch (id) {
        case DIALOG_TEXT_ENTRY:
            //This shows how to add a custom layout to an AlertDialog 
            LayoutInflater factory = LayoutInflater.from(this);
            final View textEntryView = factory.inflate(R.layout.commentlayout, null);
            return new AlertDialog.Builder(HomeActivity.this)
                .setIcon(R.drawable.ic_launcher)
                .setTitle(R.string.app_name)
                .setView(textEntryView)
                .setPositiveButton(R.string.Submit, new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {

                    postComment();

                }
            })
                .setNegativeButton(R.string.cancal, new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {
                    /* User clicked cancel so do some stuff */
                }
            }).create();
    }
    return null;
}

//this comes after the setContentView(R.Layout.view)

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view);

    public void postComment() {

        nameField = (EditText) findViewById(R.id.editText1);
        countryField = (EditText) findViewById(R.id.editText2);
        commentField = (EditText) findViewById(R.id.commentField);

        //get message from message fields
        String name = nameField.getText().toString();
        String count = countryField.getText().toString();
        String comm = commentField.getText().toString();

        //check whether the name field is empty or not
        if (name.length() > 0) {
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://_______");

            try {
                List < NameValuePair > nameValuePairs = new ArrayList < NameValuePair > (3);

                nameValuePairs.add(new BasicNameValuePair("namet", name));
                nameValuePairs.add(new BasicNameValuePair("countryt", count));
                nameValuePairs.add(new BasicNameValuePair("commentt", comm));
                httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                httpclient.execute(httppost);

                nameField.setText(""); //reset the message text field
                countryField.setText("");
                commentField.setText("");

                Toast.makeText(getBaseContext(), "Sent", Toast.LENGTH_SHORT).show();
            } catch (ClientProtocolException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {
            //display message if text field is empty
            Toast.makeText(getBaseContext(), "All fields are required", Toast.LENGTH_SHORT).show();
        }

Answer 1

只需使用以下代码替换您的nameField = (EditText) findViewById(R.id.editText1);和其他2。

nameField = (EditText) textEntryView.findViewById(R.id.editText1);
countryField = (EditText) textEntryView.findViewById(R.id.editText2);
commentField = (EditText) textEntryView.findViewById(R.id.commentField);

修改

为什么添加了textEntryView？

答案是，当您使用任何布局时，它具有 root 视图。该根视图用于根据其“资源ID”获取其子项。

当您在活动中选择两个不同的布局时，表示有两个根视图，一个由your Activity使用，可以通过ActivityName.this.findViewById()活动方法访问。但是，如果要使用其他布局，则需要添加另一个根视图的引用，该视图位于您的情况textEntryView中。所以只在那个根中搜索孩子。

Answer 2

假设以下视图来自R.layout.commentlayout

Dialog dialog=new Dialog(getApplicationContext);

替换以下内容，

nameField = (EditText) findViewById(R.id.editText1);
countryField = (EditText) findViewById(R.id.editText2);
commentField = (EditText) findViewById(R.id.commentField);

带

nameField = (EditText)dialog.findViewById(R.id.editText1);
countryField = (EditText)dialog.findViewById(R.id.editText2);
commentField = (EditText)dialog.findViewById(R.id.commentField);

尝试将Dialog表单发布到http URL时，Android Dialog显示空指针

2 个答案: