java-无法通过意图传递字符串来更改TextView的文本

概述我正在做一个非常简单的登录屏幕,用户输入用户名和密码,单击登录按钮,然后输入显示在下一个屏幕上.每次尝试更改textview值时,都会收到NullPointerException.我已经搜寻了很长一段时间,却一无所获,这很简单,我只是完全想不到.以下是我的代码：publicclassLoggedInextendsActi

我正在做一个非常简单的登录屏幕,用户输入用户名和密码,单击登录按钮,然后输入显示在下一个屏幕上.

每次尝试更改textvIEw值时,都会收到NullPointerException.我已经搜寻了很长一段时间,却一无所获,这很简单,我只是完全想不到.

以下是我的代码：

public class LoggedIn extends Activity{    String username = "";    String password = "";    TextVIEw name;    TextVIEw pwd;    button infodisp;    protected voID onCreate(Bundle savedInstanceState){        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.logged_in);        Intent intent = getIntent();        name = (TextVIEw)findVIEwByID(R.ID.username);        pwd = (TextVIEw)findVIEwByID(R.ID.password);        username = intent.getStringExtra("nameInfo");        password = intent.getStringExtra("passInfo");        name.setText(username);        pwd.setText(password);    }}

编辑：我将包更改为上面的意图,这也是其余的代码(第一个活动)

public class LoginActivity extends Activity {    button loginBtn;    button registerBtn;    EditText username;    EditText pword;    static String name;    static String pass;    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_login);        username = (EditText) this.findVIEwByID(R.ID.username);        pword = (EditText) this.findVIEwByID(R.ID.password);        loginBtn = (button) this.findVIEwByID(R.ID.loginBtn);        loginBtn.setonClickListener(new OnClickListener() {            public voID onClick(VIEw arg0){                Intent intent = new Intent(LoginActivity.this, LoggedIn.class);                name = username.getText().toString();                pass = pword.getText().toString();                intent.putExtra("nameInfo", name);                intent.putExtra("passInfo", pass);                startActivity(intent);            }        });    }

}

我没有错误地检查该值是否为null,因为这应该只是快速运行和完成的事情.我想只要在每个EditText中输入内容,字符串就不能为null,也不会有问题…对吗？

堆栈跟踪：

FATAL EXCEPTION: mainProcess: com.example.loginscreen, PID: 1677java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.loginscreen/com.example.loginscreen.LoggedIn}: java.lang.NullPointerException    at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:2176)    at androID.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)    at androID.app.ActivityThread.access0(ActivityThread.java:135)    at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)    at androID.os.Handler.dispatchMessage(Handler.java:102)    at androID.os.Looper.loop(Looper.java:137)    at androID.app.ActivityThread.main(ActivityThread.java:4998)    at java.lang.reflect.Method.invokeNative(Native Method)    at java.lang.reflect.Method.invoke(Method.java:515)    at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)    at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:593)    at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException    at com.example.loginscreen.LoggedIn.onCreate(LoggedIn.java:30)    at androID.app.Activity.performCreate(Activity.java:5243)    at androID.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)    at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:2140)    ... 11 more

Aaaand xml文件：
  activity_login：

<relativeLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"xmlns:tools="http://schemas.androID.com/tools"androID:layout_wIDth="match_parent"androID:layout_height="match_parent"androID:paddingBottom="@dimen/activity_vertical_margin"androID:paddingleft="@dimen/activity_horizontal_margin"androID:paddingRight="@dimen/activity_horizontal_margin"androID:paddingtop="@dimen/activity_vertical_margin"tools:context=".LoginActivity" ><TextVIEw    androID:ID="@+ID/textVIEw1"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignParentleft="true"    androID:text="Login:"    androID:textAppearance="?androID:attr/textAppearanceMedium" /><TextVIEw    androID:ID="@+ID/textVIEw2"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignleft="@+ID/textVIEw1"    androID:layout_below="@+ID/textVIEw1"    androID:layout_margintop="38dp"    androID:text="Password:"    androID:textAppearance="?androID:attr/textAppearanceMedium" /><EditText    androID:ID="@+ID/username"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_above="@+ID/textVIEw2"    androID:layout_alignParenttop="true"    androID:layout_marginleft="20dp"    androID:layout_toRightOf="@+ID/textVIEw1"    androID:ems="10" /><EditText    androID:ID="@+ID/password"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignBottom="@+ID/textVIEw2"    androID:layout_alignParentRight="true"    androID:layout_toRightOf="@+ID/textVIEw2"    androID:ems="10"    androID:inputType="textPassword" >    <requestFocus /></EditText><button    androID:ID="@+ID/loginBtn"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignleft="@+ID/textVIEw2"    androID:layout_below="@+ID/textVIEw2"    androID:layout_margintop="26dp"    androID:text="Login" /><button    androID:ID="@+ID/registerBtn"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignBaseline="@+ID/loginBtn"    androID:layout_alignBottom="@+ID/loginBtn"    androID:layout_alignleft="@+ID/textVIEw3"    androID:layout_marginleft="46dp"    androID:text="Register" /><CheckBox    androID:ID="@+ID/remPass"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignleft="@+ID/loginBtn"    androID:layout_below="@+ID/loginBtn"    androID:layout_margintop="19dp"    androID:text="Remember Password" /><TextVIEw    androID:ID="@+ID/textVIEw3"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_below="@+ID/remPass"    androID:layout_margintop="28dp"    androID:layout_toRightOf="@+ID/textVIEw1"    androID:text="Forgot Password" />

登录：

<relativeLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"xmlns:tools="http://schemas.androID.com/tools"androID:layout_wIDth="match_parent"androID:layout_height="match_parent"androID:paddingBottom="@dimen/activity_vertical_margin"androID:paddingleft="@dimen/activity_horizontal_margin"androID:paddingRight="@dimen/activity_horizontal_margin"androID:paddingtop="@dimen/activity_vertical_margin"tools:context=".LoginActivity" ><TextVIEw    androID:ID="@+ID/textVIEw1"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignParenttop="true"    androID:layout_centerHorizontal="true"    androID:text="Logged In!"    androID:textAppearance="?androID:attr/textAppearanceLarge" /><TextVIEw    androID:ID="@+ID/textVIEw2"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_below="@+ID/textVIEw1"    androID:layout_margintop="56dp"    androID:text="Username: "    androID:textAppearance="?androID:attr/textAppearanceLarge" /><TextVIEw    androID:ID="@+ID/textVIEw3"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignleft="@+ID/textVIEw2"    androID:layout_below="@+ID/textVIEw2"    androID:layout_margintop="56dp"    androID:text="Password: "    androID:textAppearance="?androID:attr/textAppearanceLarge" /><TextVIEw    androID:ID="@+ID/recUsername"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignBottom="@+ID/textVIEw2"    androID:layout_marginleft="33dp"    androID:layout_toRightOf="@+ID/textVIEw2"    androID:editable="true"    androID:text=" "    androID:textAppearance="?androID:attr/textAppearanceLarge" /><TextVIEw    androID:ID="@+ID/recPassword"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignBottom="@+ID/textVIEw3"    androID:layout_alignRight="@+ID/textVIEw4"    androID:editable="true"    androID:text=" "    androID:textAppearance="?androID:attr/textAppearanceLarge" /><button    androID:ID="@+ID/infoBtn"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_alignleft="@+ID/textVIEw1"    androID:layout_alignRight="@+ID/textVIEw1"    androID:layout_below="@+ID/textVIEw3"    androID:layout_margintop="62dp"    androID:text="Press to display Info" />

解决方法:

问题是因为您发现TextVIEw的ID是错误的.

    username = (TextVIEw) this.findVIEwByID(R.ID.username);    pword = (TextVIEw) this.findVIEwByID(R.ID.password);

至

    username = (TextVIEw) this.findVIEwByID(R.ID.recUsername);    pword = (TextVIEw) this.findVIEwByID(R.ID.recPassword);

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