Question

这里是产生错误的java文件“08-02 19：17：22.265：E / AndroidRuntime（17817）：java.lang.ClassCastException：android.widget.RelativeLayout无法强制转换为android.widget.TextView”

 package tip.calculator;


import android.os.Bundle;
import android.app.Activity;
import android.text.TextUtils;
import android.view.View.OnClickListener;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import android.view.View;
import android.widget.Button;




public class TipCalculator extends Activity 
{

private Button enter;
EditText myEditField ;
EditText myEditField2;
float percentage = 0;
float percentageInp = 0;
float billAmount = 0;
double output = 0; 
String output1 = "";
Button clearButton ;
TextView textView;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    myEditField = (EditText) findViewById(R.id.percentText);
    enter = (Button)findViewById(R.id.button1);
    myEditField2 = (EditText) findViewById(R.id.billText);
    clearButton = (Button) findViewById(R.id.clearButton);


    enter.setOnClickListener(new OnClickListener() {


        public void onClick(View v) {

             TextView errors;
             textView = (TextView) findViewById(R.id.textView1);
             errors = (TextView) findViewById(R.id.errorText);    



             if((myEditField2 != null) && (!TextUtils.isEmpty(myEditField2.getText().toString()))){


                percentageInp = Float.parseFloat(myEditField.getText().toString());
                billAmount = Float.parseFloat(myEditField2.getText().toString());

                percentage = ((float)percentageInp /100);

                output = (double)(billAmount * percentage);

                double result = output * 100;
                result = Math.round(result);
                result = result / 100;

                output1 = Double.toString(result);

                textView.setText(output1 + " $");

             } else{
                //Toast.makeToast(.....).show(); //Inform user about the error
             }

        }
    });

    clearButton.setOnClickListener(new OnClickListener() {

        public void onClick(View arg0) {

            percentage = 0;
            output = 0;
            output1 = "";

            TextView textView = (TextView)findViewById(R.id.errorText);
            textView.setText("");

            TextView textView2 = (TextView)findViewById(R.id.percentText);
            textView2.setText("");

            TextView textView3 = (TextView)findViewById(R.id.billText);
            textView3.setText("");


            TextView textView1 = (TextView)findViewById(R.id.textView1);
            textView1.setText("");


            percentageInp = 0;
            billAmount = 0;

            myEditField.clearComposingText();
            myEditField2.clearComposingText();

        }


    });
}
}

这里是logcat错误，我不明白它为什么会发生...

08-02 19:17:22.265: E/AndroidRuntime(17817): java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to android.widget.TextView
08-02 19:17:22.265: E/AndroidRuntime(17817):    at tip.calculator.TipCalculator$1.onClick(TipCalculator.java:48)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at android.view.View.performClick(View.java:3620)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at android.view.View$PerformClick.run(View.java:14292)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at android.os.Handler.handleCallback(Handler.java:605)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at android.os.Handler.dispatchMessage(Handler.java:92)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at android.os.Looper.loop(Looper.java:137)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at android.app.ActivityThread.main(ActivityThread.java:4507)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at java.lang.reflect.Method.invokeNative(Native Method)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at java.lang.reflect.Method.invoke(Method.java:511)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
08-02 19:17:22.265: E/AndroidRuntime(17817):    at dalvik.system.NativeStart.main(Native Method)

这里是包含所有textViews的xml，抱歉花了一段时间......

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/errorText"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:onClick="onEnterClick" >

    <EditText
        android:id="@+id/billText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:ems="10"
        android:hint="Bill Amount"
         android:inputType="numberDecimal"
        android:singleLine="true" />

    <EditText
        android:id="@+id/percentText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/billText"
        android:layout_below="@+id/billText"
        android:ems="10"
        android:hint="Percent"
        android:inputType="number"
        android:singleLine="true" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/percentText"
        android:layout_centerHorizontal="true"
        android:text="Calculate" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/percentText"
        android:layout_toRightOf="@+id/billText"
        android:text="$"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/percentText"
        android:layout_alignLeft="@+id/textView2"
        android:text="%"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Button
        android:id="@+id/clearButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button1"
        android:layout_centerHorizontal="true"
        android:text="Clear" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/textView3"
        android:layout_below="@+id/clearButton"
        android:text="Solution Will Appear Here"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

Answer 1

这里有很多错误。您必须匹配代码中的xml视图类型。

errors = (RelativeLayout)findViewById(R.id.errorText);
EditText textView3 = (EditText)findViewById(R.id.billText);
EditText textView2 = (EditText)findViewById(R.id.percentText);

我不确定你在这里要做什么，但TextView必须被强制转换为TextView＆＃39; s。 EditText必须转换为EditText。等...

<强>已更新

告诉我你正在膨胀的xml文件。其中一个视图ID用于RelativeLayout，您尝试将其强制转换为TextView。

其中一个R.id用于RelativeLayout：

textView = (TextView) findViewById(R.id.textView1);
errors = (TextView)findViewById(R.id.errorText);
TextView textView = (TextView)findViewById(R.id.errorText);
TextView textView2 = (TextView)findViewById(R.id.percentText);
TextView textView3 = (TextView)findViewById(R.id.billText);
TextView textView1 = (TextView)findViewById(R.id.textView1);

Answer 2

您无法在java中将字符串与==或!=进行比较，而是使用.equals()

if(myEditField2.getText().toString().equals("")) && (!TextUtils.isEmpty(myEditField2.getText().toString())))

希望有所帮助。

LogCat错误，为什么会发生这种情况？

2 个答案: