android - 无法解析方法 setVisibilty(int)

Question

我是 Android 开发新手。我正在尝试创建一个单击按钮的 Activity 方法。

下面是我的 MainActivity.java 文件代码。 我收到错误

1."cannot resolve method'setVisibility (int)'"  and
2."cannot resolve symbol 'TextView'"

请指导。

MainActivity.java

package com.AndroidLove;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View; 
import android.view.ViewGroup;
import android.os.Build;

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {            

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                     .add(R.id.container, new PlaceholderFragment())
                     .commit();
        }
    }
    public void onLoveButtonClicked(View view) {
        TextView textView =(TextView) findViewById(R.id.textView);
        textView.setVisibility(View.VISIBLE);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        //Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.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.
        switch (item.getItemId()) {
            case R.id.action_settings:
            return true;
        }
        return super.onOptionsItemSelected(item);
    } 
    /**
    * A placeholder fragment containing a simple view.
    */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
    }

}

Answer 1

也导入这个包

 import android.widget.TextView;