《DialogFragment系列一之源码分析》
《DialogFragment系列二之Dialog封装》
《DialogFragment系列三之AlertDialog实现》
《DialogFragment系列四之StatusDialog(Progress、Success、Error)实现》
《DialogFragment系列五之ItemDialog(eg:BottomDialog)实现》
《DialogFragment系列六之常见问题》
Android日常开发中，每一个APP都有使用弹框来进行交互的需求，最常用的有Dialog、PopUpWindow、Toast、SnackBar，有交互的操作最常用的还是Dialog，Android API已经为开发者提供了AlertDialog，相比不少读者都在使用它，但是AlertDialog有一个很大的缺点就是不受Activity/Fragment生命周期的管理，很容易出现Crash，而且屏幕切换以后还不能自动保留状态等，所以Android提供了另一个DialogFragment专门来解决这些问题，而且Google和阿里Android开发手册中都推荐使用DialogFrgament，不推荐使用AlertDialog或其他自定义AlertDialog。
下面就从DialogFragment的优点和使用来展开，想来想去还是直接从源码分析比较直观和有说服力。
源码如下：
public class DialogFragment extends Fragment
implements DialogInterface.OnCancelListener, DialogInterface.OnDismissListener {
/** @hide */
@RestrictTo(LIBRARY_GROUP)
@IntDef({STYLE_NORMAL, STYLE_NO_TITLE, STYLE_NO_FRAME, STYLE_NO_INPUT})
@Retention(RetentionPolicy.SOURCE)
private @interface DialogStyle {}
public static final int STYLE_NORMAL = 0;
public static final int STYLE_NO_TITLE = 1;
public static final int STYLE_NO_FRAME = 2;
public static final int STYLE_NO_INPUT = 3;
private static final String SAVED_DIALOG_STATE_TAG = "android:savedDialogState";
private static final String SAVED_STYLE = "android:style";
private static final String SAVED_THEME = "android:theme";
private static final String SAVED_CANCELABLE = "android:cancelable";
private static final String SAVED_SHOWS_DIALOG = "android:showsDialog";
private static final String SAVED_BACK_STACK_ID = "android:backStackId";
int mStyle = STYLE_NORMAL;
int mTheme = 0;
boolean mCancelable = true;
boolean mShowsDialog = true;
int mBackStackId = -1;
Dialog mDialog;
boolean mViewDestroyed;
boolean mDismissed;
boolean mShownByMe;
public DialogFragment() {
}
public void setStyle(@DialogStyle int style, @StyleRes int theme) {
mStyle = style;
if (mStyle == STYLE_NO_FRAME || mStyle == STYLE_NO_INPUT) {
mTheme = android.R.style.Theme_Panel;
}
if (theme != 0) {
mTheme = theme;
}
}
public void show(FragmentManager manager, String tag) {
mDismissed = false;
mShownByMe = true;
FragmentTransaction ft = manager.beginTransaction();
ft.add(this, tag);
ft.commit();
}
public int show(FragmentTransaction transaction, String tag) {
mDismissed = false;
mShownByMe = true;
transaction.add(this, tag);
mViewDestroyed = false;
mBackStackId = transaction.commit();
return mBackStackId;
}
public void showNow(FragmentManager manager, String tag) {
mDismissed = false;
mShownByMe = true;
FragmentTransaction ft = manager.beginTransaction();
ft.add(this, tag);
ft.commitNow();
}
public void dismiss() {
dismissInternal(false);
}
public void dismissAllowingStateLoss() {
dismissInternal(true);
}
void dismissInternal(boolean allowStateLoss) {
if (mDismissed) {
return;
}
mDismissed = true;
mShownByMe = false;
if (mDialog != null) {
mDialog.dismiss();
}
mViewDestroyed = true;
if (mBackStackId >= 0) {
getFragmentManager().popBackStack(mBackStackId,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
mBackStackId = -1;
} else {
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.remove(this);
if (allowStateLoss) {
ft.commitAllowingStateLoss();
} else {
ft.commit();
}
}
}
public Dialog getDialog() {
return mDialog;
}
@StyleRes
public int getTheme() {
return mTheme;
}
public void setCancelable(boolean cancelable) {
mCancelable = cancelable;
if (mDialog != null) mDialog.setCancelable(cancelable);
}
/**
* Return the current value of {@link #setCancelable(boolean)}.
*/
public boolean isCancelable() {
return mCancelable;
}
public void setShowsDialog(boolean showsDialog) {
mShowsDialog = showsDialog;
}
/**
* Return the current value of {@link #setShowsDialog(boolean)}.
*/
public boolean getShowsDialog() {
return mShowsDialog;
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (!mShownByMe) {
// If not explicitly shown through our API, take this as an
// indication that the dialog is no longer dismissed.
mDismissed = false;
}
}
@Override
public void onDetach() {
super.onDetach();
if (!mShownByMe && !mDismissed) {
// The fragment was not shown by a direct call here, it is not
// dismissed, and now it is being detached... well, okay, thou
// art now dismissed. Have fun.
mDismissed = true;
}
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mShowsDialog = mContainerId == 0;
if (savedInstanceState != null) {
mStyle = savedInstanceState.getInt(SAVED_STYLE, STYLE_NORMAL);
mTheme = savedInstanceState.getInt(SAVED_THEME, 0);
mCancelable = savedInstanceState.getBoolean(SAVED_CANCELABLE, true);
mShowsDialog = savedInstanceState.getBoolean(SAVED_SHOWS_DIALOG, mShowsDialog);
mBackStackId = savedInstanceState.getInt(SAVED_BACK_STACK_ID, -1);
}
}
@Override
@NonNull
public LayoutInflater onGetLayoutInflater(@Nullable Bundle savedInstanceState) {
if (!mShowsDialog) {
return super.onGetLayoutInflater(savedInstanceState);
}
mDialog = onCreateDialog(savedInstanceState);
if (mDialog != null) {
setupDialog(mDialog, mStyle);
return (LayoutInflater) mDialog.getContext().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
}
return (LayoutInflater) mHost.getContext().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
}
/** @hide */
@RestrictTo(LIBRARY_GROUP)
public void setupDialog(Dialog dialog, int style) {
switch (style) {
case STYLE_NO_INPUT:
dialog.getWindow().addFlags(
WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE);
// fall through...
case STYLE_NO_FRAME:
case STYLE_NO_TITLE:
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
}
}
@NonNull
public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
return new Dialog(getActivity(), getTheme());
}
@Override
public void onCancel(DialogInterface dialog) {
}
@Override
public void onDismiss(DialogInterface dialog) {
if (!mViewDestroyed) {
// Note: we need to use allowStateLoss, because the dialog
// dispatches this asynchronously so we can receive the call
// after the activity is paused. Worst case, when the user comes
// back to the activity they see the dialog again.
dismissInternal(true);
}
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (!mShowsDialog) {
return;
}
View view = getView();
if (view != null) {
if (view.getParent() != null) {
throw new IllegalStateException(
"DialogFragment can not be attached to a container view");
}
mDialog.setContentView(view);
}
final Activity activity = getActivity();
if (activity != null) {
mDialog.setOwnerActivity(activity);
}
mDialog.setCancelable(mCancelable);
mDialog.setOnCancelListener(this);
mDialog.setOnDismissListener(this);
if (savedInstanceState != null) {
Bundle dialogState = savedInstanceState.getBundle(SAVED_DIALOG_STATE_TAG);
if (dialogState != null) {
mDialog.onRestoreInstanceState(dialogState);
}
}
}
@Override
public void onStart() {
super.onStart();
if (mDialog != null) {
mViewDestroyed = false;
mDialog.show();
}
}
@Override
public void onSaveInstanceState(@NonNull Bundle outState) {
super.onSaveInstanceState(outState);
if (mDialog != null) {
Bundle dialogState = mDialog.onSaveInstanceState();
if (dialogState != null) {
outState.putBundle(SAVED_DIALOG_STATE_TAG, dialogState);
}
}
if (mStyle != STYLE_NORMAL) {
outState.putInt(SAVED_STYLE, mStyle);
}
if (mTheme != 0) {
outState.putInt(SAVED_THEME, mTheme);
}
if (!mCancelable) {
outState.putBoolean(SAVED_CANCELABLE, mCancelable);
}
if (!mShowsDialog) {
outState.putBoolean(SAVED_SHOWS_DIALOG, mShowsDialog);
}
if (mBackStackId != -1) {
outState.putInt(SAVED_BACK_STACK_ID, mBackStackId);
}
}
@Override
public void onStop() {
super.onStop();
if (mDialog != null) {
mDialog.hide();
}
}
/**
* Remove dialog.
*/
@Override
public void onDestroyView() {
super.onDestroyView();
if (mDialog != null) {
mViewDestroyed = true;
mDialog.dismiss();
mDialog = null;
}
}
}
DialogFragment是个什么东东？
我们看到DialogFragment直接继承自Fragment，但是实现了DialogInterface.OnCancelListener, DialogInterface.OnDismissListener，这俩接口熟悉不？再看里面onCreateDialog这个方法，我们可以发现DialogFragment就是Dialog和Fragment的合体。
为什么DialogFragment可以解决Dialog不能保存状态的问题？
状态数据保存：
@Override
public void onSaveInstanceState(@NonNull Bundle outState) {
super.onSaveInstanceState(outState);
if (mDialog != null) {
Bundle dialogState = mDialog.onSaveInstanceState();
if (dialogState != null) {
outState.putBundle(SAVED_DIALOG_STATE_TAG, dialogState);
}
}
if (mStyle != STYLE_NORMAL) {
outState.putInt(SAVED_STYLE, mStyle);
}
if (mTheme != 0) {
outState.putInt(SAVED_THEME, mTheme);
}
if (!mCancelable) {
outState.putBoolean(SAVED_CANCELABLE, mCancelable);
}
if (!mShowsDialog) {
outState.putBoolean(SAVED_SHOWS_DIALOG, mShowsDialog);
}
if (mBackStackId != -1) {
outState.putInt(SAVED_BACK_STACK_ID, mBackStackId);
}
}
状态保存数据取出:
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mShowsDialog = mContainerId == 0;
if (savedInstanceState != null) {
mStyle = savedInstanceState.getInt(SAVED_STYLE, STYLE_NORMAL);
mTheme = savedInstanceState.getInt(SAVED_THEME, 0);
mCancelable = savedInstanceState.getBoolean(SAVED_CANCELABLE, true);
mShowsDialog = savedInstanceState.getBoolean(SAVED_SHOWS_DIALOG, mShowsDialog);
mBackStackId = savedInstanceState.getInt(SAVED_BACK_STACK_ID, -1);
}
}
状态数据取出后直接复制给成员变量，这样全局只要使用到就可设置相关属性，这样就达到了状态保存的目的，其实就是使用了Fragment状态保存机制(savedInstanceState)
为什么DialogFragment的生命周期可控呢？
@Override
public void onStart() {
super.onStart();
if (mDialog != null) {
mViewDestroyed = false;
mDialog.show();
}
}
@Override
public void onStop() {
super.onStop();
if (mDialog != null) {
mDialog.hide();
}
}
/**
* Remove dialog.
*/
@Override
public void onDestroyView() {
super.onDestroyView();
if (mDialog != null) {
// Set removed here because this dismissal is just to hide
// the dialog -- we don't want this to cause the fragment to
// actually be removed.
mViewDestroyed = true;
mDialog.dismiss();
mDialog = null;
}
}
public int show(FragmentTransaction transaction, String tag) {
mDismissed = false;
mShownByMe = true;
transaction.add(this, tag);
mViewDestroyed = false;
mBackStackId = transaction.commit();
return mBackStackId;
}
从源码中可以看出，Dialog的显示、隐藏和销毁分别在Fragment的onStart()、onStop()、onDestroyView()中做了处理，而我们看DialogFragment的show方法需要传入FragmentTransaction参数，也就是说DialogFragment完全受FragmentManager的管理即生命周期就普通Fragment无异，所以Dialog就被Fragment给“控制”了，就再也不会出现放浪不羁的情形了！
DialogFragment怎样使用？
public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
return new Dialog(getActivity(), getTheme());
}
从源码中发现了这样一个方法，就是这个方法提供Dialog，所以我们可以通过重写这个方法来自定义DialogFragment，例如可以直接将AlertDialog写进去，其实这是体现了DialogFragment的Dialog属性，那么既然是Fragment，那就可以通过Fragment一个布局实现自定义（因为不重写onCreateDialog的话有默认）即重写onCreateView()来实现，这就是自定义DialogFragment主要的两个方法。
好了，针对DialogFragment的分析和使用就到这里吧，如果你还是使用普通的Dialog的话赶紧换成DialogFragment吧，省心省力省事！！！
