view not attached to windows manager與This Toast was not created with Toast.makeText()

標籤：android   blog   http   os   ar   cti   div   代碼   

 http://blog.sina.com.cn/s/blog_474928c90100x871.html  public class Ex04_1Activity extends Activity {   EditText editText;TextView textView;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        editText = (EditText) findViewById(R.id.myEditText);        textView = (TextView) findViewById(R.id.myTextView);        editText.setOnKeyListener(new OnKeyListener() {@Overridepublic boolean onKey(View arg0, int arg1, KeyEvent arg2) {textView.setText(editText.getText());Toast toast = new Toast(Ex04_1Activity.this);toast.setView(textView);//錯誤1toast.show();return false;}});    }}錯誤1的地方會報view not attached to windows manager的錯誤。根據錯誤提示，將代碼改為如下就可行了：@Overridepublic boolean onKey(View arg0, int arg1, KeyEvent arg2) {textView.setText(editText.getText());Toast toast = new Toast(Ex04_1Activity.this);TextView textView1 = new TextView(Ex04_1Activity.this);textView1.setText(textView.getText());toast.setView(textView1);toast.show();return false;}由此分析，以findViewById形式產生的View，new Toast()這種方式是拿不到的，因為初始程式還會報告一個FindViewLocked的錯誤。為了進一步證明我的猜想，將代碼改成如下形式：public boolean onKey(View arg0, int arg1, KeyEvent arg2) {textView.setText(editText.getText());Toast.makeText(Ex04_1Activity.this, editText.getText(), 1).show();return false;}程式又一次通過了。再次改一下代碼：public boolean onKey(View arg0, int arg1, KeyEvent arg2) {textView.setText(editText.getText());Toast toast = new Toast(Ex04_1Activity.this);    toast.setText(editText.getText().toString());toast.show();return false;}這時又報了一個：This Toast was not created with Toast.makeText()的錯誤。 

由此可見，Toast.makeText()產生的Toast可以訪問findViewById方式產生的View，而自己New Toast()的方式產生的Toast只能訪問同樣new 出來的View對象。原因大概是在.xml中產生的View對象可以被多個Activity引用，Android為了安全起見，就將其上了鎖，並且提供唯一的Toast方式，Toast.makeText()來實現吐絲，這一點和單例模式頗有共同之處