1、首先打开日程管理系统，主要看看java包和.xml,熟悉一下代码要实现具体功能。你可以发现，这个java程序全都放在一个包里，当然，这个是一个小的程序，java程序还不算太多。要是可以更加的规范，把实现不能功能的java程序分别打包，那就更好了。

2、然后找到程序的入口，在AndroidManifest中有很多你建的activity，其中有个特殊的就是intent-filer这个就是表示你这个程序的入口，那么我们这个工程的入口就是

WelcomeActivity，接下来我们就去看WelcomeActivity

3、查看欢迎界面的xml和WelcomeActivity，找出是否有错误

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package com.example.tasks;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;

import com.avos.avoscloud.AVUser;//第三方云库

public class WelcomeActivity extends Activity {

Handler handler = new Handler();

//调转到登录界面
Runnable runnable = new Runnable() {

    public void run() {Intent intent = new Intent(WelcomeActivity.this, LoginActivity.class);startActivity(intent);finish();}};
//调转到主界面
Runnable runnable1 = new Runnable() {public void run() {Intent intent = new Intent(WelcomeActivity.this, MainActivity.class);startActivity(intent);finish();}};@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_welcome);AVUser currentUser = AVUser.getCurrentUser();//加载第三方云库handler.postDelayed(runnable,2000);//闪频维持二十秒再次跳转至登录界面//以下的是错误的地方的修改，之前没有这段代码，所以欢迎界面显示不出来if (currentUser != null) {// 跳转到首页，handler.postDelayed(runnable1, 2000);} else {//缓存用户对象为空时，可打开用户注册界面…handler.postDelayed(runnable, 2000);}}

}
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4、现在阅读注册界面java代码** RegistActivity**

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public class RegistActivity extends Activity {
EditText RegistName;
EditText RegistPwd;
EditText RegistPwd2;
Button Regist;
String RName;
String RPwd;
String RPwd2;
String regist;

@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_regist);RegistName = (EditText) findViewById(R.id.RegistName);RegistPwd = (EditText) findViewById(R.id.RegistPwd);RegistPwd2 = (EditText) findViewById(R.id.RegistPwd2);Regist = (Button) findViewById(R.id.Regist);// 修改状态栏颜色，4.4+生效if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {setTranslucentStatus();}SystemBarTintManager tintManager = new SystemBarTintManager(this);tintManager.setStatusBarTintEnabled(true);tintManager.setStatusBarTintResource(R.drawable.iphone);//通知栏所需颜色Regist.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubRName = RegistName.getText().toString();RPwd = RegistPwd.getText().toString();RPwd2 = RegistPwd2.getText().toString();//这个if少了个异常处理的，如果都为空，报错if (!"".equals(RName) && !"".equals(RPwd) && !"".equals(RPwd2)) {if (!RPwd.equals(RPwd2)) {Toast.makeText(RegistActivity.this, "两次输入的密码不一致", Toast.LENGTH_LONG).show();} else {AVUser user = new AVUser();// 新建 AVUser 对象实例user.setUsername(RName);// 设置用户名user.setPassword(RPwd);// 设置密码user.signUpInBackground(new SignUpCallback() {@Overridepublic void done(AVException e) {if (e == null) {// 注册成功Toast.makeText(RegistActivity.this, "注册成功", Toast.LENGTH_LONG).show();Handler handler = new Handler();Runnable runnable = new Runnable() {@Overridepublic void run() {// TODO Auto-generated method stubIntent intent = new Intent(RegistActivity.this, LoginActivity.class);startActivity(intent);finish();}};handler.postDelayed(runnable, 2000);} else {// 失败的原因可能有多种，常见的是用户名已经存在。Toast.makeText(RegistActivity.this, "用户名已存在", Toast.LENGTH_LONG).show();}}});}}else {//加个报错的ToastToast.makeText(RegistActivity.this, "账号密码不能为空", Toast.LENGTH_LONG).show();}}});}private void setTranslucentStatus() {Window window = this.getWindow();// Translucent status barwindow.setFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS,WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
}

}

修改完运行结果如下

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5、用户注册完之后，数据库里就有了用户的账号，然后点击登录，以下是修改的代码

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public class LoginActivity extends Activity {
TextView LoginName;
TextView LoginPwd;
Button Login;
TextView Regist1;
String LN;
String LP;

@Override
protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_login);LoginName=(TextView) findViewById(R.id.LoginName);LoginPwd=(TextView) findViewById(R.id.LoginPwd);Login=(Button) findViewById(R.id.Login);Regist1=(TextView) findViewById(R.id.Regist1);// 修改状态栏颜色，4.4+生效if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {setTranslucentStatus();}SystemBarTintManager tintManager = new SystemBarTintManager(this);tintManager.setStatusBarTintEnabled(true);tintManager.setStatusBarTintResource(R.drawable.iphone);//通知栏所需颜色Login.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubLN=LoginName.getText().toString();LP=LoginPwd.getText().toString();//云数据库，使用此类AVUser.logInInBackground(LN, LP, new LogInCallback<AVUser>() {@Overridepublic void done(AVUser avUser, AVException e) {//判断是否为空，此处错误，只有if语句，缺少else语句，做出个Toastif (avUser!=null) {Intent intent=new Intent(LoginActivity.this, MainActivity.class);startActivity(intent);finish();}else{Toast.makeText(LoginActivity.this, "账号密码不能为空", Toast.LENGTH_LONG).show();}}});}});Regist1.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubIntent intent=new Intent(LoginActivity.this,RegistActivity.class);startActivity(intent);}});
}private void setTranslucentStatus() {Window window = this.getWindow();// Translucent status barwindow.setFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS,WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
}

}
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以下是修改过之后的运行结果