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我是新來的android，並在基礎應用程序中遇到錯誤。我收到以下錯誤，Android新手 - 異常 - 無法投射到android.widget.EditText
造成的：java.lang.ClassCastException：android.widget.RelativeLayout 不能轉換到android.widget.EditText在 com.example.chris.mytestv1.MainActivity.onCreate （MainActivity.java:39）
下面是該行使其
numberTxt = (EditText) findViewById(R.id.numberTxt);
在我MainActivity.java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content_main.xml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>
我搜索了爲什麼這個錯誤可能發生，但是我無法找出原因。
您的numberText是RelativeLayout項目，它不是EditText。正如錯誤所述。有什麼不清楚的？ –