SharedPreferences布尔值的一些问题

Question

I had three class, menu.class, level1.class, level2.class.

I had the following main.xml data

<Button
    android:id="@+id/f1"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_marginRight="10dp"
    android:background="@drawable/button1" />

<ImageView
    android:id="@+id/f2lock"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_marginLeft="10dp"
    android:layout_marginRight="10dp"
    android:src="@drawable/levellocked" />

<Button
    android:id="@+id/f2"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:layout_marginLeft="10dp"
    android:layout_marginRight="10dp"
    android:background="@drawable/button2"
    android:visibility="gone" />

I has the following main.class data

f1 =(Button)findViewById(R.id.f1);      
f1.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v){
        Intent i =new Intent(getApplicationContext(), level1.class);
        startActivity(i);            
    }             
}); 
f2=(Button)findViewById(R.id.f2)
f2.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v){
        Intent i =new Intent(getApplicationContext(), level2.class);
        startActivity(i);            
    }             
});   

The condition of f2 button is GONE, so in level1.class

if(answer.equalsIgnoreCase("8"))
    SharedPreferences preferences = getSharedPreferences("preferences", MODE_PRIVATE);
boolean levelTwoUnlocked = preferences.getBoolean("f2");

if(levelTwoUnlocked){
    f2.setVisibility(View.VISIBLE);
    f2lock.setVisibility(View.GONE);
}
    else {
    f2.setVisibility(View.GONE);
    f2lock.setVisibility(View.VISIBLE);
} 

It's mean f2 button setVisibility(View.VISIBLE) but I got this error in boolean levelTwoUnlocked = preferences.getBoolean("f2");

The method getBoolean(String, boolean) in the type SharedPreferences is not applicable for the arguments (String)

UPDATED.

i had changed the code like this

if(answer.equalsIgnoreCase("8"))
    SharedPreferences preferences = getSharedPreferences("preferences", MODE_PRIVATE);
    boolean levelTwoUnlocked = preferences.getBoolean("f2", false);

if(levelTwoUnlocked){
    f2.setVisibility(View.VISIBLE);
    f2lock.setVisibility(View.GONE);
}
    else {
    f2.setVisibility(View.GONE);
    f2lock.setVisibility(View.VISIBLE);
} 

but the game was force close, did the placement of the code in the wrong class? because i put the code above in level1.class not in menu.class

Answer 1

This is the android documentation.

public abstract boolean getBoolean (String key, boolean defValue)

Retrieve a boolean value from the preferences.

Parameters

key: The name of the preference to retrieve.

defValue: Value to return if this preference does not exist.

Returns

Returns the preference value if it exists, or defValue. Throws ClassCastException if there is a preference with this name that is not a boolean.

Now your problem:

It clearly says you need to pass a default value too.

Change your call like this

boolean levelTwoUnlocked = preferences.getBoolean("f2", false); // or true according to your default value

PS: Please don't think I am being rude, but you should look for the documentation at least once when error clearly say method definition is not matching or in any other such case.