Eclipse（Android）：无法解析为类型/变量等

嘿，更新Eclipse（Help -> Check for Updates）和Android-SDK-Manager之后，我总是收到“ ...无法解析为类型”或“ ...无法解析为变量”的消息。在我已经创建的每个项目以及新项目中，我都会收到此错误消息。

我已经尝试过这些东西，但是没有一个适合我：

1. Project -> Clean...
2. Right click at the project -> Properties -> Java Build Path -> Libraries -> Add Library... -> JRE System Library 我的应用程序在更新eclipse和adt后无法运行
3. Window -> Preferences -> Java -> Compiler -> Building -> [x] Rebuild class files modified by others

所有这三个步骤都无法解决这些错误消息...也许其他人知道该怎么办？重新安装Eclipse应该是最后的选择……将Eclipse与GitHub连接永远永远困扰着我：

示例代码：

package com.example.test;

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends ActionBarActivity {

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

    @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.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

错误讯息：

ActionBarActivity cannot be resolved to a type  MainActivity.java   /TestProject/src/com/example/test   line 7  Java Problem
ActionBarActivity cannot be resolved to a type  MainActivity.java   /TestProject/src/com/example/test   line 11 Java Problem
ActionBarActivity cannot be resolved to a type  MainActivity.java   /TestProject/src/com/example/test   line 31 Java Problem
error: Error retrieving parent for item: No resource found that matches the given name 'Theme.AppCompat.Light.DarkActionBar'.   styles.xml  /TestProject/res/values-v14 line 8  Android AAPT Problem
error: Error retrieving parent for item: No resource found that matches the given name 'Theme.AppCompat.Light'. styles.xml  /TestProject/res/values line 7  Android AAPT Problem
error: Error retrieving parent for item: No resource found that matches the given name 'Theme.AppCompat.Light'. styles.xml  /TestProject/res/values-v11 line 7  Android AAPT Problem
R cannot be resolved to a variable  MainActivity.java   /TestProject/src/com/example/test   line 12 Java Problem
R cannot be resolved to a variable  MainActivity.java   /TestProject/src/com/example/test   line 18 Java Problem
R cannot be resolved to a variable  MainActivity.java   /TestProject/src/com/example/test   line 28 Java Problem
The method getMenuInflater() is undefined for the type MainActivity MainActivity.java   /TestProject/src/com/example/test   line 18 Java Problem
The method onCreate(Bundle) of type MainActivity must override or implement a supertype method  MainActivity.java   /TestProject/src/com/example/test   line 10 Java Problem
The method onCreateOptionsMenu(Menu) of type MainActivity must override or implement a supertype method MainActivity.java   /TestProject/src/com/example/test   line 16 Java Problem
The method onOptionsItemSelected(MenuItem) of type MainActivity must override or implement a supertype method   MainActivity.java   /TestProject/src/com/example/test   line 23 Java Problem