Question

我正在尝试开发一个简单的应用来查找给定日期的日

xml代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.android.dayfinder.MainActivity">

    <ImageView
        android:id="@+id/image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="fitXY"
        android:src="@drawable/bg" />

    <LinearLayout
        android:id="@+id/l1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <TextView
                android:id="@+id/date"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="24dp"
                android:fontFamily="sans-serif-condensed"
                android:text="Date:"
                android:textColor="@android:color/black"
                android:textSize="35dp" />

            <TextView
                android:id="@+id/month"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="24dp"
                android:fontFamily="sans-serif-condensed"
                android:text="Month:"
                android:textColor="@android:color/black"
                android:textSize="35dp" />

            <TextView
                android:id="@+id/year"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="24dp"
                android:fontFamily="sans-serif-condensed"
                android:text="Year:"
                android:textColor="@android:color/black"
                android:textSize="35dp" />


        </LinearLayout>

        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="vertical">

            <EditText
                android:id="@+id/editText1"
                android:layout_width="120dp"
                android:layout_height="0dp"
                android:layout_marginBottom="24dp"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginTop="38dp"
                android:layout_weight="1"
                android:background="@android:color/white"
                android:fontFamily="sans-serif-condensed"
                android:hint="Enter Date"
                android:inputType="date"
                android:maxLength="2"
                android:textAlignment="gravity"
                android:textColor="@android:color/black"
                android:textColorHint="@android:color/black"
                android:textSize="20dp">

                <requestFocus />
            </EditText>

            <EditText
                android:id="@+id/editText2"
                android:layout_width="120dp"
                android:layout_height="0dp"
                android:layout_marginBottom="24dp"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginTop="40dp"
                android:layout_weight="1"
                android:background="@android:color/white"
                android:fontFamily="sans-serif-condensed"
                android:hint="Enter Month!"
                android:inputType="date"
                android:maxLength="2"
                android:textAlignment="gravity"
                android:textColor="@android:color/black"
                android:textColorHint="@android:color/black"
                android:textSize="20dp">

                <requestFocus />
            </EditText>

            <EditText
                android:id="@+id/editText3"
                android:layout_width="120dp"
                android:layout_height="0dp"
                android:layout_marginBottom="24dp"
                android:layout_marginLeft="24dp"
                android:layout_marginRight="24dp"
                android:layout_marginTop="41dp"
                android:layout_weight="1"
                android:background="@android:color/white"
                android:fontFamily="sans-serif-condensed"
                android:hint="Enter Year!"
                android:inputType="date"
                android:maxLength="4"
                android:textAlignment="gravity"
                android:textColor="@android:color/black"
                android:textColorHint="@android:color/black"
                android:textSize="20dp">

                <requestFocus />
            </EditText>
        </LinearLayout>
    </LinearLayout>

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_bel="@android:color/white"
        android:onClick="chow="@id/l1"
    android:layout_centerHorizontal="true"
    android:text="Find"
    android:layout_margin="24dp"
    android:backgroundeck"/>

    <TextView
        android:id="@+id/answer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true"
        android:layout_margin="48dp"
        android:fontFamily="sans-serif-condensed"
        android:text="Answer"
        android:textColor="@android:color/black"
        android:textSize="40dp" />

</RelativeLayout>

MainActivity.java

package com.example.android.dayfinder;

    import android.os.Bundle;
    import android.support.v7.app.AppCompatActivity;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    import source.dayfinder;

    public class MainActivity extends AppCompatActivity {
    int e1;
        String s1,s2,s3;
        private EditText medit1;
        private EditText medit2;
        private EditText medit3;
        private TextView mText;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }




    Button mbutton=(Button)findViewById(R.id.button);
        public void check(View view) {
            medit1=(EditText)findViewById(R.id.editText1);
            medit2=(EditText)findViewById(R.id.editText2);
            medit3=(EditText)findViewById(R.id.editText3);
            mText = (TextView)findViewById(R.id.answer);

            s1=medit1.getText().toString();
            s2=medit2.getText().toString();
            s3=medit3.getText().toString();
            dayfinder f=new dayfinder();
            f.finder(s1,s2,s3);
            mText.setText(f.finder(s1,s2,s3));
    }
    }

package dayfinder.java （我在mainactivity.java中使用）

 package source;

        public class dayfinder {

            public String finder(String a1, String a2, String a3) {

                int q, w, x;
                String e1;
                q = Integer.parseInt(a1);
                if ((q < 1000) || (q > 4000)) {
                    e1 = "error";
                    return e1;

                }
                else
                {
                    e1="null";
                    return e1;
                }
            }
        }

Answer 1

重新格式化您的 MainActivity.java ，如果您在此之后有任何错误，请更新您的问题

遵循命名惯例

将dayfinder对象创建转移到onCreate，以避免每次调用check方法时都创建新对象

package com.example.android.dayfinder;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import source.dayfinder;

public class MainActivity extends AppCompatActivity {
    int e1;
    String s1,s2,s3;
    private EditText medit1;
    private EditText medit2;
    private EditText medit3;
    private TextView mText ;
    private Button mbutton;
    private  dayfinder f;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initializeViews();
        f=new dayfinder();
    }


    public void initializeViews(){
        mbutton=(Button)findViewById(R.id.button);
        medit1=(EditText)findViewById(R.id.editText1);
        medit2=(EditText)findViewById(R.id.editText2);
        medit3=(EditText)findViewById(R.id.editText3);
        mText = (TextView)findViewById(R.id.answer);
    }


    public void check(View view) {
        s1=medit1.getText().toString();
        s2=medit2.getText().toString();
        s3=medit3.getText().toString();

        f.finder(s1,s2,s3);
        mText.setText(f.finder(s1,s2,s3));
    }

}

尝试在空对象引用上调用虚方法'android.view.Window $ Callback android.view.Window.getCallback（）'

1 个答案: