1.新建BaseActivity继承FragmenytActivity。由于我习惯在Activity里用些公共的方法，所以将此类建为abstract 

public abstract class BaseActivity extends FragmentActivity {}

2.重写onCreate()方法

public abstract class BaseActivity extends FragmentActivity {             @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_base_activity);    }}

3.编写必要的属性

public abstract class BaseActivity extends FragmentActivity {        protected int mScreenWidth;    protected int mScreenHeight;    protected float mDensity;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_base_activity);                        DisplayMetrics metrics =new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(metrics);        mScreenHeight = metrics.heightPixels;        mScreenWidth = metrics.widthPixels;        mDensity = metrics.density;            }}

4.编写子类公共的方法

protected void showShortToast(int resId){        Toast.makeText(this, getString(resId), Toast.LENGTH_SHORT).show();    }    protected void showShortToast(String text){        Toast.makeText(this, text, Toast.LENGTH_SHORT).show();    }        protected void showLongToast(int resId){        Toast.makeText(this, getString(resId), Toast.LENGTH_LONG).show();    }        protected void showLongToast(String text){        Toast.makeText(this, text, Toast.LENGTH_LONG).show();    }        protected void showLogDebug(String tag,String msg){        Log.d(tag, msg);    }    protected void showLogError(String tag,String msg){        Log.e(tag, msg);    }            protected void startActivity(Class
      cls, Bundle bundle){        Intent intent = new Intent();        intent.setClass(this, cls);        if(bundle != null){            intent.putExtras(bundle);        }        startActivity(intent);    }        protected void startActivity(Class
      cls){        startActivity(cls,null);    }            protected AlertDialog showAlertDialog(String title,String message){        AlertDialog alertDialog = new AlertDialog.Builder(this)        .setTitle(title)        .setMessage(message)        .show();        return alertDialog;    }        protected AlertDialog showAlertDialog(String title,String message            ,String posistiveText            ,DialogInterface.OnClickListener onPositiveClickListener            ,String negativeText            ,DialogInterface.OnClickListener onNegativeClickListener){        AlertDialog alertDialog = new AlertDialog.Builder(this)        .setTitle(title)        .setMessage(message)        .setPositiveButton(posistiveText, onPositiveClickListener)        .setNegativeButton(negativeText, onNegativeClickListener)        .show();        return alertDialog;    }            protected void defaultFinish(){        super.finish();    }            abstract void initView();    abstract void initEvent();