Question

我是Android新手，在基本应用上遇到错误。我收到以下错误，

引起：java.lang.ClassCastException：android.widget.RelativeLayout 无法转换为android.widget.EditText com.example.chris.mytestv1.MainActivity.onCreate（MainActivity.java:39）

下面是引起它的行

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

在我的MainActivity.java中我有

package com.example.chris.mytestv1;

import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;

public class MainActivity extends AppCompatActivity {

    TextView totalTextView = null;
    EditText percentageTxt = null;
    EditText numberTxt = null;
    /**
     * ATTENTION: This was auto-generated to implement the App Indexing API.
     * See https://g.co/AppIndexing/AndroidStudio for more information.
     */
    private GoogleApiClient client;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        totalTextView = (TextView) findViewById(R.id.TotalTextView);
        percentageTxt = (EditText) findViewById(R.id.percentageTxt);
        numberTxt = (EditText) findViewById(R.id.numberTxt);


        Button calcBtn = (Button) findViewById(R.id.calcBtn);
        calcBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                float percentage = Float.parseFloat(percentageTxt.getText().toString());
                float dec = percentage / 100;
                float total = dec * Float.parseFloat(numberTxt.getText().toString());
                totalTextView.setText(Float.toString(total));
            }
        });

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onStart() {
        super.onStart();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client.connect();
        Action viewAction = Action.newAction(
                Action.TYPE_VIEW, // TODO: choose an action type.
                "Main Page", // TODO: Define a title for the content shown.
                // TODO: If you have web page content that matches this app activity's content,
                // make sure this auto-generated web page URL is correct.
                // Otherwise, set the URL to null.
                Uri.parse("http://host/path"),
                // TODO: Make sure this auto-generated app URL is correct.
                Uri.parse("android-app://com.example.chris.mytestv1/http/host/path")
        );
        AppIndex.AppIndexApi.start(client, viewAction);
    }

    @Override
    public void onStop() {
        super.onStop();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        Action viewAction = Action.newAction(
                Action.TYPE_VIEW, // TODO: choose an action type.
                "Main Page", // TODO: Define a title for the content shown.
                // TODO: If you have web page content that matches this app activity's content,
                // make sure this auto-generated web page URL is correct.
                // Otherwise, set the URL to null.
                Uri.parse("http://host/path"),
                // TODO: Make sure this auto-generated app URL is correct.
                Uri.parse("android-app://com.example.chris.mytestv1/http/host/path")
        );
        AppIndex.AppIndexApi.end(client, viewAction);
        client.disconnect();
    }
}

在我的content_main.xml中，我有 -

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.chris.mytestv1.MainActivity"
    tools:showIn="@layout/activity_main"
    android:id="@+id/numberTxt">

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="0"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="41dp"
        android:textAlignment="center"
        android:textSize="50dp"
        android:id="@+id/TotalTextView" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="What is"
        android:id="@+id/textView"
        android:layout_below="@+id/TotalTextView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="41dp"
        android:layout_marginBottom="10dp" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="numberDecimal"
        android:ems="10"
        android:id="@+id/percentageTxt"
        android:layout_below="@+id/textView"
        android:layout_centerHorizontal="true"
        android:hint="Enter Percentage"
        android:textAlignment="center" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="numberDecimal"
        android:ems="10"
        android:id="@+id/numberTxt"
        android:hint="Enter Number"
        android:textAlignment="center"
        android:layout_marginTop="48dp"
        android:layout_below="@+id/textView3"
        android:layout_alignStart="@+id/percentageTxt" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="%"
        android:id="@+id/textView2"
        android:layout_marginRight="50dp"
        android:layout_alignTop="@+id/percentageTxt"
        android:layout_toEndOf="@+id/calcBtn"
        android:paddingTop="10dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Of"
        android:id="@+id/textView3"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="CALCULATE"
        android:id="@+id/calcBtn"
        android:layout_marginTop="70dp"
        android:textSize="30dp"
        android:background="#b91313"
        android:textColor="#ffffff"
        android:layout_below="@+id/numberTxt"
        android:layout_centerHorizontal="true" />

</RelativeLayout>

我已经搜索了为什么会发生此错误，但我无法找到原因。

Answer 1

您在ids中有重复，您的RelativeLayout和EditText使用相同的ID：

class IncomingController < ApplicationController
  require 'yaml'
  def create
    # ...
    body_params = YAML.load(params['body-plain'])
    url = body_params[:url]
    description = body_params[:description]
    # ...
  end
end

所以当android尝试findViewById时，他首先尝试使用RelativeLayout而不是EditText。

Answer 2

我发现错误，愚蠢的错误。我不确定我应该在哪里看。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.chris.mytestv1.MainActivity"
    tools:showIn="@layout/activity_main"
    android:id="@+id/numberTxt">

Android新手 - 异常 - 无法转换为android.widget.EditText

2 个答案: