通過程式碼生成ImageView,並把它新增到佈局中來時，可能會遇到setId()方法，那麼它有什麼作用？

作用如下：

通過程式碼新增ImageView、TextView等控制元件時，有時候會用到RelativeLayout.LayoutParams等佈局的addRule()方法，如下程式碼：

ImageView imageView = new ImageView(this.getActivity());
imageView.setId(View.generateViewId());
...
params.addRule(RelativeLayout.BELOW, imageView.getId());
 

另附上一塊完整的程式碼，但是沒setId()，ImageView沒有ID，直接取會造成錯誤。

RelativeLayout layout = new RelativeLayout(this.getActivity());
    layout.setLayoutParams(new RelativeLayout.LayoutParams(
             LayoutParams.FILL_PARENT,
             LayoutParams.FILL_PARENT));
    layout.setBackgroundColor(Color.parseColor("#CCCDCDCD"));

    ImageView imageView = new ImageView(this.getActivity());
    RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
    params.addRule(RelativeLayout.CENTER_IN_PARENT);
    imageView.setLayoutParams(params);
    imageView.setBackgroundResource(R.drawable.create_template);

    AnimationDrawable frameAnimation = (AnimationDrawable) imageView.getBackground();

    if (frameAnimation != null) {
        frameAnimation.start();
    }

    TextView textView = new TextView(this.getActivity());
    params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
    params.addRule(RelativeLayout.BELOW, imageView.getId());
    textView.setLayoutParams(params);
    textView.setText("Generating information...");

    layout.addView(imageView);
    layout.addView(textView);

    return layout;