第二个活动中创建的动态按钮在按下然后再次返回第二个活动时会复制

Question

我是android新手。每当我按下后退按钮进入主要活动然后再次返回第二个活动时，我的动态按钮会自动复制。

以下是我的代码：

public class MainActivity extends AppCompatActivity {

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

    public void food_btn_handler(View v) {
        Intent intent = new Intent(this, FoodActivity.class);
        startActivity(intent);
    }
}

//第二次活动

public class FoodActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_food);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        loadFoodStatic();
        createButtonsForFoods();
    }
}

public class FoodActivity extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_food);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        loadFoodStatic();
        createButtonsForFoods();
    }

    private void createButtonsForFoods() {
        ArrayList<Food> foods = Food.getFoods();
        LinearLayout layout = (LinearLayout) findViewById(R.id.layout_food);
        for (final Food f : foods) {
            Button b = new Button(this);
            b.setText(f.getTitle());
            layout.addView(b);
            b.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(FoodActivity.this, DetailedActivity.class);
                    intent.putExtra("rid", f.getResid());
                    intent.putExtra("title", f.getTitle());
                    intent.putExtra("desc", f.getDescription());
                    intent.putExtra("moreinfo", f.getMoreinfo_url());
                    intent.putExtra("lat", f.getLatitude());
                    intent.putExtra("lng", f.getLongitude());
                    intent.putExtra("mark", f.getMarker());
                    intent.putExtra("temp", f.getTemperature());
                    intent.putExtra("cond", f.getCondition());
                    intent.putExtra("weather", f.getWeather_url());
                    startActivity(intent);  //start activity
                }
            });
        }
    }

    private void loadFoodStatic() {

        Food.getFoods().add(new Food(R.drawable.pic1, "Food Title1","Food     Description1","http://www.food1.com",-34.0,151.0,"Marker1",11.1,"Text1",     "http://www.weather1.com"));
        Food.getFoods().add(new Food(R.drawable.pic2, "Food Title2", "Food     Description2","http://www.food2.com",2.222222,222.222222,"Marker2",22.2,"Text2",     "http://www.weather2.com"));
        Food.getFoods().add(new Food(R.drawable.pic3, "Food Title3", "Food     Description3","http://www.food3.com",3.333333,333.333333,"Marker3",33.3,"Text3",     "http://www.weather3.com"));
        Food.getFoods().add(new Food(R.drawable.pic4, "Food Title4", "Food     Description4","http://www.food4.com",4.444444,444.444444,"Marker4",44.4,"Text4",     "http://www.weather4.com"));
    }
}

Answer 1

那是因为你每次都通过调用loadFoodStatic来添加Foods。由于ArrayList / Foods是静态/单一的，它保持在调用之间，每次创建第二个活动时，每次都会添加四个相同类型的食物。

获取fixit的一种简单方法是先在loadFoodStatic中添加空列表检查：

if (Foods.getFoods().isEmpty)  {
    ... //add foods here only
}