Java 单击按钮后文本不更改

我需要一些android编程帮助。所以，点击按钮，我调用icite方法。基本上，当单击按钮时，所有文本框文本都会转换为一个新变量上的字符串。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总数。然而，它只是使我的应用程序崩溃。你知道我会做错什么吗？ 我的日志：

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

---

您的视图会导致

nullpointerexception

，因为它们是

R.layout.引文

非按钮视图的一部分。因此，在onclick之外定义以下视图

        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);

而且您还忘记初始化editText2，所以也可以将其初始化为

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

i、 e.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);
        }
    });

---

我同意@Giru Bhai，组件视图必须在创建视图时在

OnCreate（）

方法中定义，而不是在任何其他方法中定义，因此此块只能定义一次：

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);

我相信当您将标签引文文本的内容设置为authorFirst1时会出现错误，并且连接可能会得到改进

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);

---

如果不使用数组，则得到NullPointerException的唯一原因是当您寻址到代码无法识别的视图时。一旦开始编写

OnCreate（）

方法，所有视图都必须声明为布局的一部分

请发布日志猫错误。您是否在

引文.xml

布局中定义

按钮10

？@RifatRashid您忘记初始化editText2，因此也将其初始化为

editText2=（EditText）findViewById（R.id.editText2）参见编辑的答案。
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);