奇怪的ClassCastException：android.widget.textview

Question

我正在使用谷歌货币api来转换货币。但是我遇到了一个奇怪的类强制转换异常，无法弄清正在发生什么。

我发布了整个xml：

<include
    android:id="@+id/footer"
    layout="@layout/footer" />

<include
    android:id="@+id/header"
    layout="@layout/header" />

<ScrollView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@id/footer"
    android:layout_below="@id/header" >

    <RelativeLayout
        android:id="@+id/rlbody"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="18dp"
        android:background="#ffffff" >

        <RelativeLayout
            android:id="@+id/rlfrom"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="15dp" >

            <Spinner
                android:id="@+id/from_currency"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txtfromtext"
                android:background="@drawable/spinner_bg" />

         <TextView
                android:id="@+id/txtfromtext"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentTop="true"
                android:layout_centerHorizontal="true"
                android:text="From Currency:"
                android:textSize="18sp"
                android:textStyle="bold" /> 
        </RelativeLayout>

        <RelativeLayout
            android:id="@+id/rlto"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/rlfrom"
            android:layout_marginTop="20dp" >

            <TextView
                android:id="@+id/txttotext"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerHorizontal="true"
                android:text="To Currency:"
                android:textSize="18sp"
                android:textStyle="bold" /> 

            <Spinner
                android:id="@+id/to_currency"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txttotext"
                android:background="@drawable/spinner_bg" />
        </RelativeLayout>

        <RelativeLayout
            android:id="@+id/rlexchangeamt"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/rlto"
            android:layout_marginTop="20dp" >

            <TextView
                android:id="@+id/txtamt"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerHorizontal="true"
                android:text="Exchange Amount:"
                android:textSize="18sp"
                android:textStyle="bold" />

            <EditText
                android:id="@+id/input_amount"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:layout_below="@+id/txtamt"
                android:layout_margin="3dp"
                android:background="@drawable/editbackground"
                android:gravity="center" />
        </RelativeLayout>

        <LinearLayout
            android:id="@+id/lv_button"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/rlexchangeamt"
            android:orientation="horizontal"
            android:weightSum="1" >

            <Button
                android:id="@+id/convert"
                android:layout_width="30dp"
                android:layout_height="wrap_content"
                android:layout_margin="10dp"
                android:layout_weight="0.5"
                android:background="#9d1515"
                android:padding="12dp"
                android:text="Calculate"
                android:textColor="#ffffff"
                android:textSize="18sp"
                android:textStyle="bold" />

            <Button
                android:id="@+id/clear_input"
                android:layout_width="30dp"
                android:layout_height="wrap_content"
                android:layout_margin="10dp"
                android:layout_weight="0.5"
                android:background="#181818"
                android:padding="12dp"
                android:text="Reset"
                android:textColor="#ffffff"
                android:textSize="18sp"
                android:textStyle="bold" />
        </LinearLayout>

        <TextView
            android:id="@+id/output_amount"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/lv_button"
            android:layout_marginTop="10dp"
            android:gravity="center"
            android:paddingBottom="5dp"
            android:paddingRight="5dp"
            android:paddingTop="5dp"
            android:text="hello"
            android:textColor="#9d1515"
            android:textSize="20sp"
            android:textStyle="bold" />
    </RelativeLayout>
</ScrollView>

具有讽刺意味的是： 仅在我插入scrollview之后才显示 classcast异常。在此之前，一切都很好。

相关代码：

public class CurrencyConverterActivity extends Activity implements
OnClickListener, OnItemSelectedListener, TextWatcher {
    private static final String TAG = "UnitConverterActivity";
    TextView tvheader;
    private Spinner fromCurrency;
    private Spinner toCurrency;
    private EditText inputAmount;
    private TextView outputAmount, tv_header;
    private View convert;
    private View reverseCurrencies;
    private View clearInput;
    private CurrencyConverter currencyConverter;
    Activity mBaseActivity;
    String namearray[];
    List<Currency> curr ;
     String fromcode,tocode;
     ImageButton btnback;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
        WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.currency_converter);
        btnback=(ImageButton)findViewById(R.id.btn_back);
        btnback.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent i=new Intent(CurrencyConverterActivity.this,MainActivity.class);
                startActivity(i);
                finish();
            }
        });
        tvheader=(TextView)findViewById(R.id.tv_pagetitle);
        tvheader.setText("Currency Converter");
        Bitmap bmp = BitmapFactory.decodeResource(getResources(),     R.drawable.pattern_bg);
        BitmapDrawable bitmapDrawable = new BitmapDrawable(bmp);
        bitmapDrawable.setTileModeXY(Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
        RelativeLayout rl = (RelativeLayout)findViewById(R.id.rl_main);
        rl.setBackgroundDrawable(bitmapDrawable);
            curr = new ArrayList<Currency>();
    //A     
            curr.add(new Currency("United Arab Emirates Dirham(AED)","AED"));
            curr.add(new Currency("Afghan Afghani(AFN)","AFN"));
            curr.add(new Currency("Albanian Lek(ALL)","ALL"));
            curr.add(new Currency("Armenia Dram(AMD)","AMD"));
            curr.add(new Currency("Netherlands Antilles Guilder(ANG)","ANG"));
            curr.add(new Currency("Angola Kwanza(AOA)","AOA"));
            curr.add(new Currency("Argentina Peso(ARS)","ARS"));
            curr.add(new Currency("Australia Dollar(AUD)","AUD"));
            curr.add(new Currency("Aruba Guilder(AWG)","AWG"));





          namearray=new String[curr.size()];
          for(int i=0;i<curr.size();i++)  
          {  
            Currency item = curr.get(i);
            namearray[i]=item.getName();
          }

            ArrayAdapter<String> adapter=new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item,namearray);
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);



        this.fromCurrency = (Spinner) super.findViewById(R.id.from_currency);
        this.fromCurrency.setOnItemSelectedListener(this);
        fromCurrency.setAdapter(adapter);



        this.toCurrency = (Spinner) super.findViewById(R.id.to_currency);
        this.toCurrency.setOnItemSelectedListener(this);
        toCurrency.setAdapter(adapter);


        this.inputAmount = (EditText) super.findViewById(R.id.input_amount);
        this.inputAmount.setText("1");
        this.inputAmount.addTextChangedListener(this);

        this.outputAmount = (TextView) super.findViewById(R.id.output_amount);

        this.convert = super.findViewById(R.id.convert);
        this.convert.setOnClickListener(this);


        this.clearInput = super.findViewById(R.id.clear_input);
        this.clearInput.setOnClickListener(this);


        this.currencyConverter = new GoogleCurrencyConverter();
    }

LogCat：

09-23 10:43:50.876: E/AndroidRuntime(1693): FATAL EXCEPTION: main
09-23 10:43:50.876: E/AndroidRuntime(1693): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.webguru.calculatorapp/com.webguru.calculatorapp.CurrencyConverterActivity}: java.lang.ClassCastException: android.widget.TextView
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1740)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1759)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.ActivityThread.access$1500(ActivityThread.java:155)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:999)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.os.Handler.dispatchMessage(Handler.java:130)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.os.Looper.loop(SourceFile:351)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.ActivityThread.main(ActivityThread.java:3826)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at java.lang.reflect.Method.invokeNative(Native Method)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at java.lang.reflect.Method.invoke(Method.java:538)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:969)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:727)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at dalvik.system.NativeStart.main(Native Method)
09-23 10:43:50.876: E/AndroidRuntime(1693): Caused by: java.lang.ClassCastException: android.widget.TextView
09-23 10:43:50.876: E/AndroidRuntime(1693):     at com.webguru.calculatorapp.CurrencyConverterActivity.onCreate(CurrencyConverterActivity.java:373)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1082)
09-23 10:43:50.876: E/AndroidRuntime(1693):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1704)
09-23 10:43:50.876: E/AndroidRuntime(1693):     ... 11 more

行号373：this.toCurrency =（Spinner）super.findViewById（R.id.to_currency）;

我完全不知道我在这里做什么错。

Answer 1

尝试将super.findViewById更改为应该执行的findViewById 。

希望能帮助到你 ：）

Answer 2

找不到tv_pagetitle。 查看您的xml中是否有名为tv_pagetitle的textview。

Answer 3

试试这个变化，

 fromCurrency = (Spinner) findViewById(R.id.from_currency);

我在您的XML表格中找不到tv_pagetitle，请检查一下。

 tvheader=(TextView)findViewById(R.id.tv_pagetitle);

Answer 4

您没有在xml文件中提及此textview ID。

tvheader=(TextView)findViewById(R.id.tv_pagetitle);

最好改变

this.outputAmount = (TextView) super.findViewById(R.id.output_amount)

至

outputAmount = (TextView)findViewById(R.id.output_amount)