Question

在尝试运行我的应用程序时，我注意到有一些错误声称许多变量无法解析，即使在代码中声明了我将其更改为以下代码，但是一旦我进入应用程序，它就会崩溃：

public String GetErr(){

        String error="";
        if(Facebook_name.toString().equals("")&& Facebook_chk.isChecked())//check with title if not available.
        {
        error+="facebook account not entered/n";//also check if not available
        }
        if(Name.toString().equals(""))
            error+="Name not entered/n";
        if(Id.toString().contains("[a-zA-Z]+") || Id.toString().equals(""))
            error+="Id entered is invalid/n";
        if(Pass.toString().length()<5 || Pass.toString().equals(""))
            error+="Passwords must contain 5 or more digits";
    //  int day= Date.getDayOfMonth();
    //  int month = Date.getMonth();
    //  int year=Date.getYear();
        //Calendar enter = Calendar.getInstance();
    //  Calendar today = Calendar.getInstance();
    //  enter.set(year,month,day);
    //  today.set(Calendar.YEAR,Calendar.MONTH,Calendar.DAY_OF_MONTH);
        //if((enter.getTime().before(today.getTime())))
        //  error+="Date entered either passed or not available.";

        return error;
}

编辑：现在geterr（）始终返回一个空字符串。

Answer 1

您在onCreate()方法中声明变量，因此这是它们的范围。您不能在此功能之外使用它们。因此，当您在GetErr()方法中使用它们时，会出现错误。您可以通过将多个方法中所需的变量移动到全局变量来解决此问题（因此在类中而不是在方法中声明它们。

修改

package com.example.app; //import java.util.Calendar; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.CheckBox; import android.widget.CompoundButton; //import android.widget.DatePicker; import android.widget.TextView; public class Second extends Activity implements OnClickListener { CheckBox Facebook_chk; TextView Facebook_name; TextView Name; TextView Id; TextView Txterr; TextView Pass; Button Btn1; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.setContentView(R.layout.second); Btn1 = (Button) findViewById(R.id.Btn1); Facebook_chk = (CheckBox)findViewById(R.id.Cfbook);//Represents the facebook checkbox. Facebook_name = (TextView)findViewById(R.id.Face);//represents the facebook text. Name = (TextView)findViewById(R.id.Name);//represents the Name text. Id = (TextView)findViewById(R.id.Id);//represents the Id text. Txterr = (TextView)findViewById(R.id.Txterr);//represents the Id text. Pass = (TextView)findViewById(R.id.Pass);//represents the Pass text. Btn1.setOnClickListener(this); Facebook_chk.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener(){ @Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { // TODO Auto-generated method stub if(Facebook_chk.isChecked()) Facebook_name.setEnabled(true); else Facebook_name.setEnabled(false); ; } }); } public String GetErr(){ String error=""; if(Facebook_name==null && Facebook_chk.isChecked())//check with title if not available. { error+="facebook account not entered/n";//also check if not available } if(Name==null) error+="Name not entered/n"; if(Id.toString().contains("[a-zA-Z]+") || Id==null) error+="Id entered is invalid/n"; if(Pass.toString().length()<5) error+="Passwords must contain 5 or more digits"; // int day= Date.getDayOfMonth(); // int month = Date.getMonth(); // int year=Date.getYear(); //Calendar enter = Calendar.getInstance(); // Calendar today = Calendar.getInstance(); // enter.set(year,month,day); // today.set(Calendar.YEAR,Calendar.MONTH,Calendar.DAY_OF_MONTH); //if((enter.getTime().before(today.getTime()))) // error+="Date entered either passed or not available."; return error; } @Override public void onClick(View v) { if(v == Btn1){ String err = GetErr(); if(err != ""){ Txterr.setText(err); } } } }

Answer 2

定义：

CheckBox Facebook_chk
TextView Facebook_name
TextView Name
TextView Id 
TextView Txterr
TextView Pass

作为全局变量，例如：

public class Second extends Activity implements OnClickListener {

    CheckBox Facebook_chk;
    TextView Facebook_name;
    TextView Name;
    TextView Id;
    TextView Txterr;
    TextView Pass;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        this.setContentView(R.layout.second);

         Facebook_chk = (CheckBox)findViewById(R.id.Cfbook);//Represents the facebook checkbox.
         Facebook_name = (TextView)findViewById(R.id.Face);//represents the facebook text.
         Name = (TextView)findViewById(R.id.Name);//represents the Name text.
         Id = (TextView)findViewById(R.id.Id);//represents the Id text.
         Txterr = (TextView)findViewById(R.id.Txterr);//represents the Id text.
         Pass = (TextView)findViewById(R.id.Pass);//represents the Pass text.

...
}
...
}

更新：

如果您想要View回复点击事件，则需要确保将View设置为可点击。

自从你做到了：

View v = findViewById(R.id.Btn1);
v.setOnClickListener((OnClickListener) this);

我不知道R.id.Btn1真的是Button还是View。如果是Button，请更改为：

Button button = findViewById(R.id.Btn1);
button.setOnClickListener(this);

如果它不是一个按钮，只有一些View，并且您希望它回复您的点击，请在findViewById之后添加一行

v.setClickable(true);

同样，如果您打算稍后在代码中使用此v，则需要将其声明为全局变量，就像您在TextView上所做的那样

参考public void setClickable (boolean clickable)

Android变量可用性（无法解决）

2 个答案: