Question

所以，我的代码给我带来了以下错误

01-30 15:30:09.658: E/AndroidRuntime(8705): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gameproj/com.example.gameproj.InvScreen}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.addView(android.view.View)' on a null object reference

它说它在

行

((RelativeLayout) findViewById(R.layout.activity_inv_screen)).addView(sv);

我不确定如何修复它。

以下是相关代码。

Protag hero = MainActivity.hero;
ArrayList<ItemBase> invn;
ArrayList<Button> bt;
int i = 0;
int j = 0;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_inv_screen);
    setScreen();
}

public void setScreen(){

    RelativeLayout rl = (RelativeLayout) findViewById(R.layout.activity_inv_screen);
    RelativeLayout layout = new RelativeLayout(this);
    HashMap<String, ArrayList<ItemBase>> items = hero.getStuff();
    ScrollView sv = new ScrollView(this);

    for (Entry<String, ArrayList<ItemBase>> entry : items.entrySet()){
         String key = entry.getKey();
         ArrayList<ItemBase> value = entry.getValue();

         for (ItemBase item: value){
             bt.add(new Button(this));
             bt.get(i).setText(key);
             layout.addView(bt.get(i));
             invn.add(item);
             bt.get(i).setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    j = i;

                }
            });
             i++;
         }
    }
    ((RelativeLayout) findViewById(R.layout.activity_inv_screen)).addView(sv);
    sv.addView(layout);

}

Answer 1

两次更改

更改

RelativeLayout rl = (RelativeLayout) findViewById(R.layout.activity_inv_screen);

到

RelativeLayout rl = (RelativeLayout) findViewById(R.id.activity_inv_screen); // use its id not layout

然后改变

((RelativeLayout) findViewById(R.layout.activity_inv_screen)).addView(sv);

到

rl.addView(sv);

使用findviewbyid的addview视图和null

1 个答案: