Android-使用xml文件资源定义菜单

public class MainActivity extends AppCompatActivity {
    private TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView) findViewById(R.id.txt);
        // 为文本框注册上下文菜单
        registerForContextMenu(textView);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = new MenuInflater(this);
        //装填R.Menu.my_menu菜单，并添加到menu中
        inflater.inflate(R.menu.menu_main,menu);
        return super.onCreateOptionsMenu(menu);
    }
    //创建上下文菜单时触发该方法
    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        MenuInflater inflater = new MenuInflater(this);
        //装填R.Menu.menu菜单，并添加到menu中
        inflater.inflate(R.menu.context,menu);
        menu.setHeaderIcon(R.drawable.seek02);
        menu.setHeaderTitle("请选择背景色");
    }
    //上下文菜单中菜单项被单击时，触发该方法

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        //勾选菜单项
        item.setChecked(true);
        switch (item.getItemId()){
            case R.id.red:
                item.setChecked(true);
                textView.setBackgroundColor(Color.RED);
                break;
            case R.id.green:
                item.setChecked(true);
                textView.setBackgroundColor(Color.GREEN);
                break;
            case R.id.blue:
                item.setChecked(true);
                textView.setBackgroundColor(Color.BLUE);
                break;
        }
        return true;
    }
    //菜单项被单击后的回调方法

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.isCheckable()){
            //勾选菜单项
            item.setCheckable(true);
        }
        //switch 判断单击哪个菜单项，并有针对性的做出响应
        switch (item.getItemId()){
            case R.id.font_10:
                textView.setTextSize(10 * 2);
                break;
            case R.id.font_12:
                textView.setTextSize(12 * 2);
                break;
            case R.id.font_14:
                textView.setTextSize(14 * 2);
                break;
            case R.id.font_16:
                textView.setTextSize(16 * 2);
                break;
            case R.id.font_18:
                textView.setTextSize(18 * 2);
                break;
            case R.id.red_font:
                textView.setTextColor(Color.RED);
                break;
            case R.id.green_font:
                textView.setTextColor(Color.GREEN);
                break;
            case R.id.blue_font:
                textView.setTextColor(Color.BLUE);
                break;
        }
        return true;
    }
}