Question

我正在尝试通过用户的活动获取联系号码（已选中）。如何解决这个问题？强制关闭而不是输出！我已经阅读了很多教程，但这对我没那么有用！

  package com.example.c_p;


    import java.util.Iterator;
    import java.util.Set;

    import android.app.Activity;
    import android.content.Intent;
    import android.database.Cursor;
    import android.net.Uri;
    import android.os.Bundle;
    import android.provider.ContactsContract.CommonDataKinds.Phone;
    import android.provider.ContactsContract.Contacts;
    import android.util.Log;
    import android.view.View;
    import android.widget.EditText;
    import android.widget.Toast;

    public class MainActivity extends Activity {
        private static final int CONTACT_PICKER_RESULT = 1001;
    public static final String DEBUG_TAG = null;
         EditText emailEntry = (EditText) findViewById(R.id.invite_email);
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }
        public void doLaunchContactPicker(View view)
        {
        Intent contactPickerIntent = new Intent(Intent.ACTION_PICK,
                Contacts.CONTENT_URI);
        startActivityForResult(contactPickerIntent, CONTACT_PICKER_RESULT);
    }
        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data)
        {
            if (resultCode == RESULT_OK) {
                switch (requestCode)
                {
                case CONTACT_PICKER_RESULT:
                    Cursor cursor = null;
                    String phone = "";
                    try {
                        Bundle extras = data.getExtras();
                        Set<String> keys = extras.keySet();
                        Iterator<String> iterate = keys.iterator();
                        while (iterate.hasNext()) {
                            String key = iterate.next();
                            Log.v(DEBUG_TAG, key + "[" + extras.get(key) + "]");
                        }

                        Uri result = data.getData();
                        Log.v(DEBUG_TAG, "Got a contact result: "
                                + result.toString());

                        // get the contact id from the Uri
                        String id = result.getLastPathSegment();


                        cursor = getContentResolver().query(Phone.CONTENT_URI,
                                null, Phone.CONTACT_ID + "=?", new String[] { id },
                                null);

                        int PhoneIdx = cursor.getColumnIndex(Phone.DATA);


                        if (cursor.moveToFirst()) {
                                         phone = cursor.getString(PhoneIdx);

                            Log.v(DEBUG_TAG, "Got number: " + phone);

                        } else {
                            Log.w(DEBUG_TAG, "No results");
                        }
                    } catch (Exception e) {
                        Log.e(DEBUG_TAG, "Failed to Number", e);
                    } 
                    finally {
                        if (cursor != null) {
                            cursor.close();
                        }

                        emailEntry.setText(phone);

                        if (phone.length() == 0) {
                            Toast.makeText(this, "No number found for contact.",
                                    Toast.LENGTH_LONG).show();
                        }

                    }

                    break;
                }

            } else {
                Log.w(DEBUG_TAG, "Warning: activity result not ok");
            }
        }
    }

Answer 1

你有这个

  EditText emailEntry = (EditText) findViewById(R.id.invite_email);

在onCreate之外。您将获得NullPointeException

更改为

private EditText emailEntry; 
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    emailEntry = (EditText) findViewById(R.id.invite_email); 
}

findViewById在当前夸大的布局中查找id为id的视图。您需要先将内容设置为活动，然后在onCreate

中初始化视图

Answer 2

这一行会给你一个错误

EditText emailEntry = (EditText) findViewById(R.id.invite_email);

在设置内容之前，您无法尝试初始化View。在setContentView()之后将其初始化为

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

    // not until here
    emailEntry = (EditText) findViewById(R.id.invite_email);

由于您的视图存在于您的布局中，因此在使用inflater或setContentView（）夸大布局之前，您无法像findViewById（）那样找到它们。

强制关闭而不是输出

2 个答案: