shared preferences是什么？就是数据的持久化，主要保存一些简单的数据在应用内部
定义变量：

private Button mButton;
private boolean mDatas;

调用函数

@Override
protected void onCreate(Bundle savedInstanceState) {      
   super.onCreate(savedInstanceState); 
   setContentView(R.layout.activity_first);  
   setData();  
   saveDataPreference(mDatas);
}

private void setData() {
    SharedPreferences sharedPreferences =FirstActivity.this.getSharedPreferences("preference_name", Context.MODE_PRIVATE);
    mDatas = sharedPreferences.getBoolean("mData", true);
    if (mDatas == false) {
        startActivity(new Intent(FirstActivity.this, MainActivity.class));       
        finish();
} 
    else {
         mButton = (Button) findViewById(R.id.button1);
         mButton.setOnClickListener(new View.OnClickListener() {    ;           
    @Override    
              public void onClick(View view) {
              startActivity(new Intent(FirstActivity.this, SecondActivity.class));          
              FirstActivity.this.finish();
              }
     });

private void saveDataPreference(boolean data){
    //系统会自动帮我们创建一个XML文件  名字是"preference_name "     
      SharedPreferences sharedPreferences = FirstActivity.this.getSharedPreferences("preference_name", Context.MODE_PRIVATE);
      SharedPreferences.Editor editor = sharedPreferences.edit();      
      editor.putBoolean("mData",false);
      editor.commit();
}