无法在Android Studio中解析符号fab

Question

I am developing an app but I am having an issue with a piece of code. The same piece of code is giving me the same error for a few different pages.

The code is as follows:

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    buttonSignIn = (Button) findViewById(R.id.buttonSignIN);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG).setAction("Action", null).show();

            buttonSignIn.setOnClickListener(this);
        }
    });
}}

It gives me an error on the line below saying it cannot resolve symbol fab FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

Answer 1

You probably deleted the fab in your activity_main:

If that's the case, and you really don't need the fab, you probably just need to delete this piece of code:

buttonSignIn = (Button) findViewById(R.id.buttonSignIN);

FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View view) {
        Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG).setAction("Action", null).show();

        buttonSignIn.setOnClickListener(this);
    }
});

Answer 2

add the support:design in build.gradle: module app to dependencies this will fix it

compile 'com.android.support:design:26.+'

will look like this :

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:26.+'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile 'com.android.support:design:26.+'
testCompile 'junit:junit:4.12'

}