android - Android填写文本字段

我不知道哪个因素可能导致此问题，因为即使在调试后，仍然无法弄清楚。问题是，在启动应用程序后，我试图用以前登录时保存的数据填充登录名和密码的文本字段。但是我无法获得对TextFields的引用：/它总是为null，为什么不呢？到目前为止，我所拥有的是。

public class Login extends ActionBarActivity {

private String SHARED_PREFS_KEY = "SBJP";
private String LOGIN_KEY = "login";
private String PASS_KEY = "pass";

private EditText userName;
private EditText password;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    PlaceholderFragment phFrag = new PlaceholderFragment();

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, phFrag)
                .commit();
    }

    loadPreferences(phFrag);

}


@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.login, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_login, container, false);
        return rootView;
    }
}

/**
 * Handles login action
 */
public void loginClick(View v){
    this.userName = (EditText) findViewById(R.id.login_screen_tf_login);
    this.password = (EditText) findViewById(R.id.login_screen_tf_password);

    String userNameStr = userName.getText().toString();
    String passStr = password.getText().toString();

    //Log.d("SB", userNameStr+":"+passStr);
    SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_KEY, MODE_PRIVATE);
    Editor editor = prefs.edit();

    editor.putString(PASS_KEY, passStr);
    editor.putString(LOGIN_KEY, userNameStr);
    editor.commit();
}

/**
 * Handles creating new account
 */
public void createNewAccountClick(View v){
    Log.d("SB", "Here comes account creation");
}

private void loadPreferences(PlaceholderFragment rootView){
    SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_KEY, MODE_PRIVATE);
    String loginStr = prefs.getString(LOGIN_KEY, null);
    String passStr = prefs.getString(PASS_KEY, null);

    this.userName = (EditText) rootView.getView().findViewById(R.id.login_screen_tf_login);
    this.password = (EditText) rootView.getView().findViewById(R.id.login_screen_tf_password);

    Log.d("SB","Login/sn:"+loginStr+passStr);

    if(loginStr != null && userName != null){
        userName.setText(loginStr);
    }
    if(passStr != null && password != null){
        password.setText(passStr);
    }

}

}

有人知道吗，为什么在loadPreferences方法中总是将userName和password变量获取为null？在loginClick方法中，它可以正常工作：/ ...

提前致谢

最佳答案

this.userName = (EditText) findViewById(R.id.login_screen_tf_login);
this.password = (EditText) findViewById(R.id.login_screen_tf_password);

在这里，您需要获取片段的根视图，但要在PlaceholderFragment类的代码内：

userName = (EditText) getView().findViewById(R.id.login_screen_tf_login);
password = (EditText) getView().findViewById(R.id.login_screen_tf_password);

http://developer.android.com/reference/android/app/Fragment.html#getView()

当然，我们建议login_screen_tf_login和login_screen_tf_login EditText-s位于fragment_login布局中。

加成：

您可以按照以下方式重新设计PlaceholderFragment：

public static class PlaceholderFragment extends Fragment {

private String login;
private String password;

public void setAuthData(String login, String password){ this.login = login; this.password = password; }

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_login, container, false);

    EditText userName = (EditText) rootView.findViewById(R.id.login_screen_tf_login);
    userName.setText(login);
    EditText passwordET = (EditText) rootView.findViewById(R.id.login_screen_tf_password);
    passwordET.setText(password);
    return rootView;
}
}

并使用PlaceholderFragment类，如下所示：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    SharedPreferences prefs = getSharedPreferences(SHARED_PREFS_KEY, MODE_PRIVATE);
    String login = prefs.getString(LOGIN_KEY, null);
    String password = prefs.getString(PASS_KEY, null);

    PlaceholderFragment phFrag = new PlaceholderFragment();
    phFrag.setAuthData(login, password);

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
            .add(R.id.container, phFrag)
            .commit();
    }
 }