Question

我有一个应用程序，其中布局顶部有一个微调器，下面有一些文本字段，底部有一个名为“RESULT”的按钮。在微调器中，我放置了不同公式的名称，选中它们时必须对文本字段中的数字起作用，当按下RESULT按钮时，必须显示带有结果的新布局。截至目前，我已经为每个微调器中的公式创建了活动。我不知道如何将微调器公式选择与公式活动相关联。作为初学者，我在这里搜索了所有可能的解决方案但却找不到它。任何人都可以帮我一块代码。

我应用了如下所示的解决方案

protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.selective);
final Class[] clazz={Srkt.class,Binkhorst.class,Srk2.class,Holladay.class};
spin=(Spinner)findViewById(R.id.formulae);
spin.setOnItemSelectedListener(new OnItemSelectedListener() {

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int pos,
            long id) {
        // TODO Auto-generated method stub
        Intent i=new Intent(Selection.this,clazz[pos]);
        startActivity(i);

    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0) {
        // TODO Auto-generated method stub

    }
    });

logcat显示以下错误

    12-28 15:17:41.336: E/Trace(768): error opening trace file: No such file or directory (2)
12-28 15:17:44.554: E/AndroidRuntime(768): FATAL EXCEPTION: main
12-28 15:17:44.554: E/AndroidRuntime(768): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.iolcalci/com.example.iolcalci.Srkt}: java.lang.NullPointerException
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.os.Looper.loop(Looper.java:137)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.ActivityThread.main(ActivityThread.java:5039)
12-28 15:17:44.554: E/AndroidRuntime(768):  at java.lang.reflect.Method.invokeNative(Native Method)
12-28 15:17:44.554: E/AndroidRuntime(768):  at java.lang.reflect.Method.invoke(Method.java:511)
12-28 15:17:44.554: E/AndroidRuntime(768):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-28 15:17:44.554: E/AndroidRuntime(768):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-28 15:17:44.554: E/AndroidRuntime(768):  at dalvik.system.NativeStart.main(Native Method)
12-28 15:17:44.554: E/AndroidRuntime(768): Caused by: java.lang.NullPointerException
12-28 15:17:44.554: E/AndroidRuntime(768):  at com.example.iolcalci.Srkt.onCreate(Srkt.java:34)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.Activity.performCreate(Activity.java:5104)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
12-28 15:17:44.554: E/AndroidRuntime(768):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
12-28 15:17:44.554: E/AndroidRuntime(768):  ... 11 more

此处的Srkt代码

public class Srkt extends Activity{
EditText k1_e,k2_e,al_e,alconst_e;
float k1,k2,al,al_const;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
     float Rcor;
     float Lcor;
     float Crwdest;
     float Avg_k;
     float Corneal_H;
     float Acd_Const;
     float Offset;
     float Acd_Est;
     float Na=(float) 1.34;
     float C2=(float) 0.33;
     float C3;
     float C4;
     float C5;
     float C6;
     float C8;
     float C9;
     float Iolam;


    k1_e=(EditText)findViewById(R.id.k1_editText);
    k1=Float.parseFloat(k1_e.getText().toString());
    k2_e=(EditText)findViewById(R.id.k2_editText);
    k2=Float.parseFloat(k2_e.getText().toString());
    al_e=(EditText)findViewById(R.id.al_editText);//line 37
    al=Float.parseFloat(al_e.getText().toString());
    alconst_e=(EditText)findViewById(R.id.al_const_editText);
    al_const=Float.parseFloat(alconst_e.getText().toString()); 


    Avg_k=(k1+k2)/2;
    float Rcor1=(float)(337.5/Avg_k);Rcor=Round(Rcor1,2);

    if(al<=24.2){
        Lcor=al;
    }else{
        Lcor=(float) (-3.446+1.716*al-0.0237*(al*al));
    }Lcor=Round(Lcor,2);
    Crwdest=(float) (-5.41+0.58412*Lcor+0.098*Avg_k);Crwdest=Round(Crwdest,2);
    Corneal_H=(float) (Rcor-(Math.sqrt(Rcor*Rcor-Crwdest*Crwdest/4)));Corneal_H=Round(Corneal_H,2);
    Acd_Const=(float) (0.62467*al_const-68.747);
    Offset=(float) (Acd_Const-3.336);Offset=Round(Offset,2);
    Acd_Est=(Corneal_H+Offset); float Acd_Est1=Round(Acd_Est,2);
    C3=(float) (0.97971*al+0.65696);C3=Round(C3,2);     
    C4=C3-Acd_Est1;C4=Round(C4,2);
    C5=(float) ((Na*Rcor)-(C2*Acd_Est)); C5=Round(C5, 2);
    C6=(float) ((Na*Rcor1)-(C2*C3));
    C8=(float) ((12*C6)+(C3*Rcor1));C8=Round(C8,2);
    C9=(float) ((12*C5)+(Acd_Est*Rcor1));C9=Round(C9,2);
    Iolam=(float) ((1336*(C6-(0.001*C8*0)))/(C4*(C5-(0.001*0*C9))));Iolam=Round(Iolam,2);                       /*Desired Refraction not taken*/
    }

    public static float Round(float Rval, int Rpl) {
          float p = (float)Math.pow(10,Rpl);
          Rval = Rval * p;
          float tmp = Math.round(Rval);
          return (float)tmp/p;
          }

我已添加此行选择活动

k1_e=(EditText)findViewById(R.id.k1_editText);
k1=Float.parseFloat(k1_e.getText().toString());

更新了logcat显示

    12-29 07:16:54.642: E/AndroidRuntime(766): FATAL EXCEPTION: main
12-29 07:16:54.642: E/AndroidRuntime(766): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.iolcalci/com.example.iolcalci.Selection}: java.lang.NumberFormatException: Invalid float: ""
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.os.Looper.loop(Looper.java:137)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.ActivityThread.main(ActivityThread.java:5039)
12-29 07:16:54.642: E/AndroidRuntime(766):  at java.lang.reflect.Method.invokeNative(Native Method)
12-29 07:16:54.642: E/AndroidRuntime(766):  at java.lang.reflect.Method.invoke(Method.java:511)
12-29 07:16:54.642: E/AndroidRuntime(766):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-29 07:16:54.642: E/AndroidRuntime(766):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-29 07:16:54.642: E/AndroidRuntime(766):  at dalvik.system.NativeStart.main(Native Method)
12-29 07:16:54.642: E/AndroidRuntime(766): Caused by: java.lang.NumberFormatException: Invalid float: ""
12-29 07:16:54.642: E/AndroidRuntime(766):  at java.lang.StringToReal.invalidReal(StringToReal.java:63)
12-29 07:16:54.642: E/AndroidRuntime(766):  at java.lang.StringToReal.parseFloat(StringToReal.java:289)
12-29 07:16:54.642: E/AndroidRuntime(766):  at java.lang.Float.parseFloat(Float.java:300)
12-29 07:16:54.642: E/AndroidRuntime(766):  at com.example.iolcalci.Selection.onCreate(Selection.java:25)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.Activity.performCreate(Activity.java:5104)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
12-29 07:16:54.642: E/AndroidRuntime(766):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
12-29 07:16:54.642: E/AndroidRuntime(766):  ... 11 more

该问题是什么以及我该如何处理它？</ strong>

Answer 1

截至目前，我已在spinner中为每个公式创建了活动。我不知道如何将微调器公式选择与公式联系起来活性。

有一个Class数组，其中包含每个Activities的名称（顺序将是Spinner中出现的公式的顺序）：

Class[] clazz = {NameOfActivity1.class, NameOfActivity2.class /*etc*/};

然后，您将拥有一个int字段（ mSelected ），该字段将由OnItemSelectedListener上的Spinner更新（ mSelected = position ）。当显示结果时，只需使用 mSelected 字段以及上面的数组即可开始正确的活动：

Intent i = new Intent(this, clazz[mSelected]);

此外，根据您在结果活动中显示的内容，您可能希望使用单个结果活动来保存包含公式的数组。对于此活动，您将从int传递当前所选公式的Intent值（在Spinner中），您将使用它来构建正确的结果输出。

Selection活动中的正确实施：

private int mSelected = -1;

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.selective);
final Class[] clazz={Srkt.class,Binkhorst.class,Srk2.class,Holladay.class};
spin=(Spinner)findViewById(R.id.formulae);
spin.setOnItemSelectedListener(new OnItemSelectedListener() {

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int pos,
            long id) {
        mSelected = pos;
    }

    @Override
    public void onNothingSelected(AdapterView<?> arg0) {
       mSelected = -1;
    }
    });
// find the results Button and set a OnClickListener where you'll do the calculation
Button resultsButton = (Button) findViewById(R.id.the_id_of_the_results_button);
resultsButton.setOnClickListener(new OnCLickListener() {

    @Override
    public void onClick(View v) {
         // In here you'll do the calculation
         // you know the selected formula from the value of mSelected
         // after you do the calculation you will start the proper results activity using the clazz array and mSelected
        // you would also pass the results you calculated in the Intent used to start the new activity
    }

});

如何将微调项目选择连接到活动？

1 个答案: