Question

我需要一些android编程帮助。所以onbutton点击我在icite方法中调用。基本上，当单击按钮时，所有文本框文本都将转换为字符串到新变量上。之后，我将所有变量组合成一个名为Total的字符串。然后我将标签textView10的文本更改为字符串Total。但它只是崩溃了我的应用程序。你知道我可能做错了什么吗？我的logcat：

11-17 03:02:43.652: W/dalvikvm(1952): threadid=1: thread exiting with uncaught exception (group=0xb1f60648)
11-17 03:02:43.662: E/AndroidRuntime(1952): FATAL EXCEPTION: main
11-17 03:02:43.662: E/AndroidRuntime(1952): java.lang.NullPointerException
11-17 03:02:43.662: E/AndroidRuntime(1952):     at com.example.randomapplication.citationsPage$1.onClick(citationsPage.java:59)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at android.view.View.performClick(View.java:4240)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at android.view.View$PerformClick.run(View.java:17721)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at android.os.Handler.handleCallback(Handler.java:730)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at android.os.Handler.dispatchMessage(Handler.java:92)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at android.os.Looper.loop(Looper.java:137)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at android.app.ActivityThread.main(ActivityThread.java:5103)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at java.lang.reflect.Method.invokeNative(Native Method)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at java.lang.reflect.Method.invoke(Method.java:525)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-17 03:02:43.662: E/AndroidRuntime(1952):     at dalvik.system.NativeStart.main(Native Method)
11-17 03:02:45.552: D/dalvikvm(1982): GC_FOR_ALLOC freed 92K, 11% free 2541K/2832K, paused 8ms, total 9ms
11-17 03:02:45.552: I/dalvikvm-heap(1982): Grow heap (frag case) to 3.277MB for 635808-byte allocation
11-17 03:02:45.562: D/dalvikvm(1982): GC_FOR_ALLOC freed <1K, 9% free 3162K/3456K, paused 11ms, total 11ms
11-17 03:02:45.572: D/dalvikvm(1982): GC_FOR_ALLOC freed <1K, 9% free 3162K/3456K, paused 4ms, total 4ms
11-17 03:02:45.572: I/dalvikvm-heap(1982): Grow heap (frag case) to 3.753MB for 500412-byte allocation
11-17 03:02:45.592: D/dalvikvm(1982): GC_FOR_ALLOC freed <1K, 8% free 3650K/3948K, paused 14ms, total 15ms
11-17 03:02:45.662: D/libEGL(1982): loaded /system/lib/egl/libEGL_emulation.so
11-17 03:02:45.662: D/(1982): HostConnection::get() New Host Connection established 0xb7acdfa0, tid 1982
11-17 03:02:45.672: D/libEGL(1982): loaded /system/lib/egl/libGLESv1_CM_emulation.so
11-17 03:02:45.682: D/libEGL(1982): loaded /system/lib/egl/libGLESv2_emulation.so
11-17 03:02:45.692: W/EGL_emulation(1982): eglSurfaceAttrib not implemented
11-17 03:02:45.702: D/OpenGLRenderer(1982): Enabling debug mode 0

代码

package com.example.randomapplication;

import java.util.Calendar;


    import android.annotation.SuppressLint;
    import android.app.Activity;
    import android.content.ClipData;
    import android.content.ClipboardManager;
    import android.content.Context;
    import android.net.Uri;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    public class citationsPage extends Activity {
    EditText editText1;
    EditText author;
    EditText articleTitle;
    EditText webTitle;
    EditText editText2;
    EditText webDay;
    EditText webMonth;
    EditText webYears;
    TextView textView10;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.citations);
        final Button citationButton = (Button) findViewById(R.id.button10);
        citationButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Calendar cal = Calendar.getInstance();
                // Gets date from the calendar!
                int day = cal.get(Calendar.DAY_OF_MONTH);
                int month = cal.get(Calendar.MONTH);
                int year = cal.get(Calendar.YEAR);

                String month1 = String.valueOf(month);
                String day1 = String.valueOf(day);
                String year1 = String.valueOf(year);

                editText1 = (EditText) findViewById(R.id.editText1);
                author = (EditText) findViewById(R.id.author);
                articleTitle = (EditText) findViewById(R.id.articleTitle);
                webTitle = (EditText) findViewById(R.id.webTitle);
                webDay = (EditText) findViewById(R.id.webDay);
                webMonth = (EditText) findViewById(R.id.webMonth);
                webYears = (EditText) findViewById(R.id.webYears);


                String authorFirst1 = editText1.getText().toString();
                String authorLast1 = author.getText().toString();
                String articleTitle1 = articleTitle.getText().toString();
                String website1 = webTitle.getText().toString();
                String Publisher1 = editText2.getText().toString();
                String month2 = webMonth.getText().toString();
                String day2 = webDay.getText().toString();
                String year2 = webYears.getText().toString();
                TextView citationText = (TextView) findViewById(R.id.textView10);
                String Total = authorLast1+","+" "+authorFirst1+"."+" "+"\""+articleTitle1+"."+"\""+" "+website1+"."+" "+Publisher1+","+" "+day2+" "+month2+" "+year2+"."+" "+"Web"+"."+" "+day+" "+month+"."+" "+year+".";
                citationText.setText(authorFirst1);



            }
        });

    }

    @SuppressLint("NewApi") public void iCite() {


        Calendar cal = Calendar.getInstance();
        // Gets date from the calendar!
        int day = cal.get(Calendar.DAY_OF_MONTH);
        int month = cal.get(Calendar.MONTH);
        int year = cal.get(Calendar.YEAR);

        String month1 = String.valueOf(month);
        String day1 = String.valueOf(day);
        String year1 = String.valueOf(year);

        editText1 = (EditText) findViewById(R.id.editText1);
        author = (EditText) findViewById(R.id.author);
        articleTitle = (EditText) findViewById(R.id.articleTitle);
        webTitle = (EditText) findViewById(R.id.webTitle);
        webDay = (EditText) findViewById(R.id.webDay);
        webMonth = (EditText) findViewById(R.id.webMonth);
        webYears = (EditText) findViewById(R.id.webYears);


        String authorFirst1 = editText1.getText().toString();
        String authorLast1 = author.getText().toString();
        String articleTitle1 = articleTitle.getText().toString();
        String website1 = webTitle.getText().toString();
        String Publisher1 = editText2.getText().toString();
        String month2 = webMonth.getText().toString();
        String day2 = webDay.getText().toString();
        String year2 = webYears.getText().toString();
        TextView citationText = (TextView) findViewById(R.id.textView10);
        String Total = authorLast1+","+" "+authorFirst1+"."+" "+"\""+articleTitle1+"."+"\""+" "+website1+"."+" "+Publisher1+","+" "+day2+" "+month2+" "+year2+"."+" "+"Web"+"."+" "+day+" "+month+"."+" "+year+".";
        citationText.setText(Total);

        /*ClipboardManager clipboard = (ClipboardManager)
        getSystemService(Context.CLIPBOARD_SERVICE);
        Uri copyUri = Uri.parse(authorLast1+","+" "+authorFirst1+"."+" "+"\""+articleTitle1+"."+"\""+" "+website1+"."+" "+Publisher1+","+" "+day2+" "+month2+" "+year2+"."+" "+"Web"+"."+" "+day+" "+month+"."+" "+year+".");
        //ClipData clip = ClipData.newPlainText(Total + "");
        ClipData clip = ClipData.newUri(getContentResolver(),"URI",copyUri);
        */


    }
}

Answer 1

您的观看次数会导致nullpointerexception，因为它们是R.layout.citations非按钮视图的一部分。因此，将以下视图定义到onclick外部

        editText1 = (EditText) findViewById(R.id.editText1);
        author = (EditText) findViewById(R.id.author);
        articleTitle = (EditText) findViewById(R.id.articleTitle);
        webTitle = (EditText) findViewById(R.id.webTitle);
        webDay = (EditText) findViewById(R.id.webDay);
        webMonth = (EditText) findViewById(R.id.webMonth);
        webYears = (EditText) findViewById(R.id.webYears);
        TextView citationText = (TextView) findViewById(R.id.textView10);

你也忘了初始化editText2，所以也把它作为

初始化

  editText2 = (EditText) findViewById(R.id.editText2);

即。将onCreate方法重写为

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.citations);
    final Button citationButton = (Button) findViewById(R.id.button10);

    editText1 = (EditText) findViewById(R.id.editText1);
    editText2 = (EditText) findViewById(R.id.editText2);
    author = (EditText) findViewById(R.id.author);
    articleTitle = (EditText) findViewById(R.id.articleTitle);
    webTitle = (EditText) findViewById(R.id.webTitle);
    webDay = (EditText) findViewById(R.id.webDay);
    webMonth = (EditText) findViewById(R.id.webMonth);
    webYears = (EditText) findViewById(R.id.webYears);
    final  TextView citationText = (TextView) findViewById(R.id.textView10);


    citationButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Calendar cal = Calendar.getInstance();
            // Gets date from the calendar!
            int day = cal.get(Calendar.DAY_OF_MONTH);
            int month = cal.get(Calendar.MONTH);
            int year = cal.get(Calendar.YEAR);

            String month1 = String.valueOf(month);
            String day1 = String.valueOf(day);
            String year1 = String.valueOf(year);

            String authorFirst1 = editText1.getText().toString();
            String authorLast1 = author.getText().toString();
            String articleTitle1 = articleTitle.getText().toString();
            String website1 = webTitle.getText().toString();
            String Publisher1 = editText2.getText().toString();
            String month2 = webMonth.getText().toString();
            String day2 = webDay.getText().toString();
            String year2 = webYears.getText().toString();
            String Total = authorLast1+","+" "+authorFirst1+"."+" "+"\""+articleTitle1+"."+"\""+" "+website1+"."+" "+Publisher1+","+" "+day2+" "+month2+" "+year2+"."+" "+"Web"+"."+" "+day+" "+month+"."+" "+year+".";
            citationText.setText(authorFirst1);
        }
    });

Answer 2

我同意@ Giru-Bhai，组件视图必须在创建视图时定义，在OnCreate()方法中，而不是在任何其他方法内，因此这个块必须只有一次：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.citations);
    editText1 = (EditText) findViewById(R.id.editText1);
    author = (EditText) findViewById(R.id.author);
    articleTitle = (EditText) findViewById(R.id.articleTitle);
    webTitle = (EditText) findViewById(R.id.webTitle);
    webDay = (EditText) findViewById(R.id.webDay);
    webMonth = (EditText) findViewById(R.id.webMonth);
    webYears = (EditText) findViewById(R.id.webYears);

现在，在线

String Total = authorLast1+","+" "+authorFirst1+"."+" "+"\""+articleTitle1+"."+"\""+" "+website1+"."+" "+Publisher1+","+" "+day2+" "+month2+" "+year2+"."+" "+"Web"+"."+" "+day+" "+month+"."+" "+year+".";
        citationText.setText(authorFirst1);

我认为将标签CitationText的内容设置为authorFirst1时会出现错误，也可能会改进连接。

String Total = authorLast1+","+" "+authorFirst1+"."+" "+"\""+articleTitle1+"."+"\""+" "+website1+"."+" "+Publisher1+","+" "+day2+" "+month2+" "+year2+"."+" "+"Web"+"."+" "+day1+" "+month1+"."+" "+year1+".";
        citationText.setText(authorFirst1);

String Total = authorLast1+", "+authorFirst1+". \""+articleTitle1+".\" "+website1+"."+Publisher1+", "+day2+" "+month2+" "+year2+". "+"Web"+". "+day1+" "+month1+". "+year1+".";
        citationText.setText(Total);

如果您不使用数组，则获得NullPointerException的唯一原因是当您寻址代码无法识别的视图时。一旦开始编写OnCreate()方法，就必须将所有视图声明为布局的一部分。

单击按钮后文本不会更改

2 个答案: