ID无法解析或不是字段

Question

I'm new to android development and I'm currently working on building a pretty basic application. I want 'button1' to open a new activity. Looked around online and I can't work out what I'm doing wrong!

Java:

package com.testtest.herro;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class FullscreenActivity extends Activity

{

Button button1, saved;

    @Override
    public void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
        {
                setContentView(R.layout.activity_fullscreen); 

            button1 = (Button) findViewById (R.id.button1);
        };

};}

I'm getting the following errors on the public void onCreate method:

• Syntax errors on token ")", { expected after this token.
• Overrides android.app.Activity.onCreate
• Syntax errors on token ")", { expected after this token.

The findViewById line has this error:

-ids cannot be resolved or is not a field.

XML:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFFFFF"
android:orientation="vertical"
tools:context="com.testtest.herro.FullscreenActivity" >

<View
    android:layout_width="1dp"
    android:layout_height="30dp" >
</View>

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="top"
    android:gravity="center"
    android:text="Idea Cloud"
    android:textSize="45sp"
    android:typeface="monospace" >
</TextView>

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="top"
    android:gravity="center"
    android:text=""
    android:textSize="45sp"
    android:textStyle="bold" >
</TextView>

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_gravity="bottom"
    android:background="#FFFFFF"
    android:orientation="vertical" >

    <View
        android:layout_width="1dp"
        android:layout_height="30dp" >
    </View>

    <Button
        android:layout_width="250sp"
        android:layout_height="100sp"
        android:layout_gravity="center"
        android:text="New"
        android:textSize="20sp"
        android:typeface="monospace"
        android:id="@+id/button1" >
    </Button>

    <View
        android:layout_width="1dp"
        android:layout_height="50dp" >
    </View>

    <Button
        android:layout_width="250sp"
        android:layout_height="100sp"
        android:layout_gravity="center"
        android:text="Saved"
        android:textSize="20sp"
        android:typeface="monospace"
        android:id="@+id/savedB" >
    </Button>
  </LinearLayout>

</LinearLayout>

Any help is greatly appreciated! Thanks.

Answer 1

Change your function to this:

public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fullscreen);
    button1 = (Button) findViewById (R.id.button1);
}

Also, to change activities make these two changes:

XML

<Button
        android:layout_width="250sp"
        android:layout_height="100sp"
        android:layout_gravity="center"
        android:text="New"
        android:textSize="20sp"
        android:typeface="monospace"
        android:id="@+id/button1"
        android:onClick="activityChange">
</Button>

Java

public void activityChange(View view) {
     //Change Activities using an Intent
    Intent intent = new Intent(this, YOUR_CLASS_NAME.class);
    startActivity(intent);
}

See these references for an explanation. This developer.android.com/training site will help you learn the basics the right way.

http://developer.android.com/reference/android/widget/Button.html http://developer.android.com/training/basics/firstapp/starting-activity.html

Answer 2

Your super call is outside the method. This:

public void onCreate(Bundle savedInstanceState) 
super.onCreate(savedInstanceState);
{
    ...
}

should be:

public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    ...
}

In general, if you start seeing lots of errors, it's worth looking at the first line containing an error - that's probably the cause. Also, save and compile often , so you can tell where you've made a mistake and fix it quickly.

Also note that you don't need semi-colons after method or class declarations - I would remove them as a matter of style.

Ideally, use @Override too, to get the compiler to check that you're really overriding a method:

@Override
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    ...
}