android - Android登录页面异常

Question

我想创建一个这样的登录页面：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="fill_parent"
    android:background="#000000" >
    <TextView
        android:id="@+id/Lbl_Title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="@string/Title"
        android:layout_margin="0dp" 
        android:padding="10dp"
        android:textColor="#FFFFFF"
        android:paddingRight="0dp"/>
    <EditText
        android:id="@+id/usrNameTxt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="textEmailAddress"
        android:hint="@string/username"
       android:layout_marginBottom="20dp"
       android:typeface="serif" 
        android:layout_alignParentLeft="true"

        android:layout_below="@id/Lbl_Title"/>
 <EditText
        android:id="@+id/usrPassTxt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp"
        android:inputType="text"
        android:hint="@string/password"

        android:typeface="serif" 
        android:layout_alignParentLeft="true"
        android:layout_below="@id/usrPassTxt" 
         />

     <Button
        android:id="@+id/Btn_exit_app"
        android:layout_width="65dp"
        android:layout_height="wrap_content"
        android:layout_below="@id/usrPassTxt"
         android:text="@string/Exit" 
        android:layout_alignParentRight="true"
        />
      <Button
        android:id="@+id/Btn_Login"
         android:layout_width="65dp"
        android:layout_height="wrap_content"
        android:layout_below="@+id/usrPassTxt"
        android:layout_toLeftOf="@id/Btn_exit_app"
         android:layout_alignBottom="@id/Btn_exit_app"
        android:text="@string/Login" />



</RelativeLayout>

这是我的代码，当用户使用正确的密码登录进入主要活动时，如果密码无效，用户应该被引导到错误页面，第二部分我的意思是错误页面很好，但第一部分没有工作并将意外停止。我将不胜感激任何建议。

package com.example.test;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.text.InputType;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.example.test.Buy;
import com.example.test.ErrorPage;


public class MyClass extends Activity {
    private EditText uName;
    private EditText uPass;
    private Button loginBtn;
    private Button Btn_Exit;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setUpViews();
        this.Btn_Exit=(Button)this.findViewById(R.id.Btn_exit_app);
       Btn_Exit.setOnClickListener(new OnClickListener() {

            public void onClick(View arg0) {

            //  android.os.Process.killProcess(android.os.Process.myPid());
                Intent _Intent =new Intent(Intent.ACTION_MAIN);
                _Intent.addCategory(Intent.CATEGORY_HOME);
                _Intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(_Intent);


            }
        });


    }
    @Override
    protected void onResume() {
        super.onResume();
        uName.setText("Enter User Name");
        uName.setTextColor(Color.parseColor("#888888"));
        uPass.setText("Enter Password");
        uPass.setInputType(InputType.TYPE_CLASS_TEXT);
        uPass.setTextColor(Color.parseColor("#888888"));
    }
    private void setUpViews() {
         uName=(EditText)findViewById(R.id.usrNameTxt);
         uPass=(EditText)findViewById(R.id.usrPassTxt);
        uName.setOnFocusChangeListener(new View.OnFocusChangeListener() {

            public void onFocusChange(View v, boolean hasFocus) {
                if(uName.getText().toString().equalsIgnoreCase("Enter User Name")){
                    if(hasFocus){
                        uName.setTextColor(Color.parseColor("#000000"));
                        uName.setText("");
                    }
                }
                else if(uName.getText().toString().equalsIgnoreCase("")){
                    uName.setTextColor(Color.parseColor("#888888"));
                    uName.setText("Enter User Name");
                }
            }
        });
        uPass.setOnFocusChangeListener(new View.OnFocusChangeListener(){

            public void onFocusChange(View v, boolean hasFocus) {
                if(uPass.getText().toString().equalsIgnoreCase("Enter Password")){
                    if(hasFocus){
                        uPass.setInputType(InputType.TYPE_CLASS_TEXT| InputType.TYPE_TEXT_VARIATION_PASSWORD);
                        uPass.setTextColor(Color.parseColor("#000000"));
                        uPass.setText("");
                    }
                }
                else if(uPass.getText().toString().equalsIgnoreCase("")){
                        uPass.setInputType(InputType.TYPE_CLASS_TEXT);
                        uPass.setTextColor(Color.parseColor("#888888"));
                        uPass.setText("Enter Password");
                }
            }
        });
        loginBtn=(Button)findViewById(R.id.Btn_Login);

        //loginBtn.setFocusableInTouchMode(true);
        loginBtn.requestFocus();
        loginBtn.setOnClickListener(new OnClickListener() {
            private String pass;
            private String name;
            Intent myIntent;

            public void onClick(View v) {
                name=uName.getText().toString();
                pass=uPass.getText().toString();
                if(name.equalsIgnoreCase("so") && pass.equalsIgnoreCase("so"))
                {
                    myIntent=new Intent(MyClass.this,Main.class);
                    System.out.println("---IF---");
                }
                else if(name.equalsIgnoreCase("so")){
                    myIntent=new Intent(MyClass.this,ErrorPage.class);
                    myIntent.putExtra("user", "ok");
                    System.out.println("---ELSE IF---");
                }
                else{
                    myIntent=new Intent(MyClass.this,ErrorPage.class);
                    System.out.println("---ELSE---");
                }
                myIntent.putExtra("value", name);
                startActivity(myIntent);
            }
        });
    }
}

这是我的日志：

    12-23 14:14:57.716: D/AndroidRuntime(226): Shutting down VM
12-23 14:14:57.726: W/dalvikvm(226): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
12-23 14:14:57.726: E/AndroidRuntime(226): Uncaught handler: thread main exiting due to uncaught exception
12-23 14:14:57.736: E/AndroidRuntime(226): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test/com.example.test.Main}: java.lang.NullPointerException
1
12-23 14:14:57.736: E/AndroidRuntime(226):  at dalvik.system.NativeStart.main(Native Method)
12-23 14:14:57.736: E/AndroidRuntime(226): Caused by: java.lang.NullPointerException
12-23 14:14:57.736: E/AndroidRuntime(226):  at com.exampletest.Main.onCreate(Main.java:52)
12-23 14:14:57.736: E/AndroidRuntime(226):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-23 14:14:57.736: E/AndroidRuntime(226):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)

这是 Main.java：

package com.example.test;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.provider.Settings.System;
import android.view.KeyEvent;
import android.view.View;
import android.view.WindowManager;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;


public class Main extends Activity {

    private Button btn_Buy;
    private Button btn_BuyExperience;
    private Button btn_Change_Password;


    Bundle myValues;
    private TextView welcomeMsg;
    //private Button backButton;

    public void onCreate(Bundle savedInstanceState) 
    {
        ///-----------------
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        this.btn_Buy=(Button)this.findViewById(R.id.Btn_Buy);
        this.btn_BuyExperience=(Button)this.findViewById(R.id.btn_Buy_Experience);
        this.btn_Change_Password=(Button)this.findViewById(R.id.btn_Change_Password);

        myValues=getIntent().getExtras();




        btn_Buy.setOnClickListener(new OnClickListener() {

            public void onClick(View arg0) {
                Intent Frm_Buy=new Intent(Main.this,Buy.class);
                startActivity(Frm_Buy);
            }
        });

        btn_BuyExperience.setOnClickListener(new OnClickListener() {

            public void onClick(View arg0) {
                Intent Frm_Buyexperience=new Intent(Main.this,current_cart.class);
                startActivity(Frm_Buyexperience);
            }
        });

        btn_Change_Password.setOnClickListener(new OnClickListener() {

            public void onClick(View arg0) {
                startActivity(new Intent(Main.this,Change_Password.class));

            }
        });
        setUpViews();
    }
      private void setUpViews() {

        welcomeMsg=(TextView)findViewById(R.id.msg);
        welcomeMsg.setText("WelcomePage : "+myValues.getString("value"));
        Button LogoutButton=(Button)findViewById(R.id.Btn_Logout);
        LogoutButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                finish();
            }
        });
    }
    @Override
    public void onAttachedToWindow() {
        this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
        super.onAttachedToWindow();

    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
       if(keyCode == KeyEvent.KEYCODE_HOME)
           Toast.makeText(getBaseContext(),
                    "Please Log Out !", Toast.LENGTH_LONG).show();
     return false;
    }

}

主要的.xml

 <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:fillViewport="true"
    android:background="#000000"
     >

<RelativeLayout 
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >


<TableLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/btn_Buy_Experience"
   android:layout_centerHorizontal="true"
      android:layout_centerVertical="true"
     >
 <TableRow android:id="@+id/tableRowWelcome"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
        <TextView
        android:id="@+id/msg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="@string/welcome"
        android:textStyle="bold"
        android:typeface="serif" />

    </TableRow>
    <TableRow
        android:id="@+id/tablerowBuy"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
        <Button
         android:id="@+id/Btn_Buy"
        android:layout_height="wrap_content"
       android:layout_weight="1"
    android:text="@string/Shop"
     android:drawableRight="@drawable/shopcartnew"
    />

    </TableRow>

    <TableRow
        android:id="@+id/tableRowCart"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
       >
        <Button
       android:id="@+id/btn_Buy_Experience"
       android:layout_height="wrap_content"
       android:layout_marginTop="20dp"
      android:layout_weight="1"
      android:text="@string/ShoppingCart"
      android:drawableRight="@drawable/shopcartico2"/>
    </TableRow>

    <TableRow
        android:id="@+id/tableRowPass"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
          android:layout_centerHorizontal="true"

         >
        <Button
        android:id="@+id/btn_Change_Password"
    android:layout_height="wrap_content"
android:layout_marginTop="20dp"
        android:layout_weight="1"
        android:text="@string/ChangePassword" 
        android:drawableRight="@drawable/passchange2"/>
    </TableRow>

    <TableRow
        android:id="@+id/tableRowLogout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >
         <Button
        android:id="@+id/Btn_Logout"
         android:layout_height="wrap_content"
       android:layout_marginTop="20dp"
        android:text="@string/logout"
         android:drawableRight="@drawable/exiticon" 
        />
    </TableRow>


</TableLayout>

</RelativeLayout>
</ScrollView>

score 0 · Accepted Answer

在看到您的main.xml文件后，您没有带有 idbtn_Buy_Experience的按钮，因此在 main.xml 中添加一个按钮：

<Button
        android:id="@+id/btn_Buy_Experience"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
 ...../>

score 0 · Accepted Answer

你的有问题setUpViews()。错误发生在：

E/AndroidRuntime(218): at com.example.test.Main.setUpViews(Main.java:53) 12-23 12:24:17.109:

将您的 setUpViews() 替换为以下代码：

    private void setUpViews() {
        this.btn_Buy=(Button)this.findViewById(R.id.Btn_Buy);
        this.btn_BuyExperience=(Button)this.findViewById(R.id.btn_Buy_Experience);
        this.btn_Change_Password=(Button)this.findViewById(R.id.btn_Change_Password);


        welcomeMsg=(TextView)findViewById(R.id.msg);
        welcomeMsg.setText("WelcomePage : "+myValues.getString("value"));
        Button LogoutButton=(Button)findViewById(R.id.Btn_Logout);
        LogoutButton.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {
                finish();
            }
        });

您试图在启动按钮之前设置按钮的 setOnClick 侦听器。

score 0 · Accepted Answer

你的有错误Main.java

注意你setupviews()之前打电话

   this.btn_Buy=(Button)this.findViewById(R.id.Btn_Buy);
    this.btn_BuyExperience=(Button)this.findViewById(R.id.btn_Buy_Experience);
    this.btn_Change_Password=(Button)this.findViewById(R.id.btn_Change_Password);

但你试图onClickListeners为他们设置setupviews()

它们此时为空，因此导致NullPointer

放在setUpViewsonCreate 的末尾。它应该工作。

 @Override
public void onCreate(Bundle savedInstanceState) 
{
    ///-----------------
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    myValues=getIntent().getExtras();

    this.btn_Buy=(Button)this.findViewById(R.id.Btn_Buy);
    this.btn_BuyExperience=(Button)this.findViewById(R.id.btn_Buy_Experience);
    this.btn_Change_Password=(Button)this.findViewById(R.id.btn_Change_Password);

    setUpViews();
}

您的代码中有错误main.XML或错误。

该错误是由于您btn_Buy_Experience在TableLayout.main.xml

您必须将其转换为 tableLayout 而不是按钮。

为了帮助使用 tableLayouts 和按钮，您可能需要查看 OnClickListener 和 Table Layout这个问题

score -1 · Accepted Answer

检查这个

if(name.equalsIgnoreCase("so") && pass.equalsIgnoreCase("so"))
                {
                    myIntent=new Intent(MyClass.this,Main.class);
                    System.out.println("---IF---");
                }
                else if(name.equalsIgnoreCase("so")){
                    myIntent=new Intent(MyClass.this,ErrorPage.class);
                    myIntent.putExtra("user", "ok");
                    System.out.println("---ELSE IF---");
                }
                else{
                    myIntent=new Intent(MyClass.this,ErrorPage.class);
                    System.out.println("---ELSE---");
                }

似乎您从未创建过myIntent对象，因为所有条件都失败了，而您得到了NullPointerException.

myIntent.putExtra("value", name);

android - Android登录页面异常

4 回答 4

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