app 被系统意外杀死(包括横竖屏切换) Activity/Fragment中的字段通过自定义注解+反射实现自动恢复
源码
当App意外被杀死，如长时间滞留后台，横竖屏切换，这时再进入app，并不是正常启动app(不会走入口流程)。
这时候Activity/Fragment 中字段就需要临时保存和恢复。
override fun onSaveInstanceState(outState: Bundle) {
super.onSaveInstanceState(outState)
//通过Bundle 保存临时数据
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if(savedInstanceState != null) {
//Bundle 重新恢复数据
}
}
上面代码比较简单，唯一的问题就是需要自己反复的保存和读取，重复代码比较多。
下面通过自定义注解和反射的方式实现字段自动恢复(可以通过开发者选项，打开不保留后台选项，模拟后台杀死app，或者横竖屏切换)
创建一个基类 BaseActivity 或者 BaseFragment
abstract class BaseActivity : Fragment(), IDisplay {
//通过 ObjectInstanceManager实现保存和恢复字段，包括恢复字段类型为fragment
private var mOIM: ObjectInstanceManager = ObjectInstanceManager()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//....
if(savedInstanceState != null) {
//重新恢复fragment
mOIM.againFragmentInstance(supportFragmentManager, this)
//重新恢复字段
mOIM.againFieldInstance(savedInstanceState, this)
}
}
override fun onSaveInstanceState(outState: Bundle) {
super.onSaveInstanceState(outState)
//保存字段
mOIM.saveField(outState, this)
}
}
使用
class MainActivity : BaseAct() {
//添加AgainFragmentInstance注解，可以重新实例化fragment
@AgainFragmentInstance
private var mainFragment: MainFragment? = null
//未指定key， 字段名作为key
@AgainInstance
private val age = 10
/**
* 可以手动指定key
*/
@AgainInstance(key = "price")
private val mPrice = 2000
//第一次正常初始化字段
override fun onInitData() {
//fragment 只要初始化一次
mainFragment = MainFragment.newInstance("this is main_fragment")
supportFragmentManager.beginTransaction().replace(R.id.contentPanel, mainFragment!!)
.commitAllowingStateLoss()
}
override fun onResume() {
super.onResume()
Timber.d("${mainFragment == null}")
Timber.d("age $age")
Timber.d("user $mUser")
Timber.d("price $mPrice")
Timber.d("userList $mUserLis")
Timber.d("userMap $mUserMap")
Timber.d("map $mMap")
}
}
实现逻辑
主要通过自定义注解来标识需要重新实例化的字段，再通过反射把字段存储到Bundle，和从Bundle重新获取重新赋值。
- @AgainInstance 标识字段
@Keep
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface AgainInstance {
/**
* 通过onSaveInstanceState保存
* 不指定key的情况使用字段名作为key
* @return key作为 Bundle的key
*/
String key() default "";
}
- 找到有@AgainInstance标识的字段，判断类型根据不同类型，存放Bundle中
public class ObjectInstanceManager {
/**
* 保存 @AgainInstance注解绑定的field
*
* @param outState 通过Bundle
* @param activityOrFragment 只能是activity或者fragment
*/
public void saveField(Bundle outState, Object activityOrFragment) {
//获取对象中的所有字段
Field[] declaredFields = activityOrFragment.getClass().getDeclaredFields();
if (declaredFields.length == 0) return;
for (Field field : declaredFields) {
//标记 AgainInstance注解的才处理
if (field.isAnnotationPresent(AgainInstance.class)) {
field.setAccessible(true);
AgainInstance annotation = field.getAnnotation(AgainInstance.class);
String key = annotation.key();
//如果没有自定义key，那么直接使用属性名
if(TextUtils.isEmpty(key)) {
key = field.getName();
}
try {
//如果字段 值为null，不处理
if (field.get(activityOrFragment) == null) continue;
//以下根据字段的不同类型，保存到Bundle中
if (field.getType() == short.class) {
outState.putShort(key, field.getShort(activityOrFragment));
} else if (field.getType() == int.class) {
outState.putInt(key, field.getInt(activityOrFragment));
} else if (field.getType() == long.class) {
outState.putLong(key, field.getLong(activityOrFragment));
} else if (field.getType() == float.class) {
outState.putFloat(key, field.getFloat(activityOrFragment));
} else if (field.getType() == double.class) {
outState.putDouble(key, field.getDouble(activityOrFragment));
} else if (field.getType() == String.class) {
outState.putString(key, (String) field.get(activityOrFragment));
} else if (!isParcelableArray(field.getType()) && isSerializable(field.getType())) {
outState.putSerializable(key, (Serializable) field.get(activityOrFragment));
} else if (isParcelable(field.getType())) {
outState.putParcelable(key, (Parcelable) field.get(activityOrFragment));
} else if (field.getType() == short[].class || field.getType() == Short[].class) {
outState.putShortArray(key, (short[]) field.get(activityOrFragment));
} else if (field.getType() == int[].class || field.getType() == Integer[].class) {
outState.putIntArray(key, (int[]) field.get(activityOrFragment));
} else if (field.getType() == long[].class || field.getType() == Long[].class) {
outState.putLongArray(key, (long[]) field.get(activityOrFragment));
} else if (field.getType() == float[].class || field.getType() == Float[].class) {
outState.putFloatArray(key, (float[]) field.get(activityOrFragment));
} else if (field.getType() == double[].class || field.getType() == Double[].class) {
outState.putDoubleArray(key, (double[]) field.get(activityOrFragment));
} else if (isParcelableArray(field.getType())) { //不支持
// Parcelable[] parcelables = (Parcelable[]) field.get(activityOrFragment);
// ArrayList<Parcelable> parcelables1 = (ArrayList<Parcelable>) Arrays.asList(parcelables);
// outState.putParcelableArrayList(key, parcelables1);
throw new RuntimeException(activityOrFragment.getClass().getName() + "--> 属性字段:" + field.getName() + " 不支持Parcelable[]类型 ");
} else if (field.getType() == List.class || field.getType() == ArrayList.class) {
saveListType(outState, activityOrFragment, field, key);
} else {
throw new RuntimeException(activityOrFragment.getClass().getName() + ": 该类型不支持" +
field.getType().getName() +
", 支持的类型 包括基本类型，基本类型包装类，实现了Serializable，Parcelable接口对象，数组，一级List集合");
}
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}
}
- 重新还原字段值
public class ObjectInstanceManager {
/**
* 重新实例化 带有@AgainInstance注解 的field
*
* @param savedInstanceState
* @param activityOrFragment
*/
public void againFieldInstance(@NonNull Bundle savedInstanceState, @NonNull Object activityOrFragment) {
Field[] declaredFields = activityOrFragment.getClass().getDeclaredFields();
if (declaredFields.length == 0) return;
for (Field field : declaredFields) {
try {
if (field.isAnnotationPresent(AgainInstance.class)) {
field.setAccessible(true);
AgainInstance annotation = field.getAnnotation(AgainInstance.class);
String key = annotation.key();
//如果没有指定key，就直接使用属性名称
if(TextUtils.isEmpty(key)) {
key = field.getName();
}
Object val = null;
if (field.getType() == short.class) {
val = savedInstanceState.getShort(key);
} else if (field.getType() == int.class) {
val = savedInstanceState.getInt(key);
} else if (field.getType() == long.class) {
val = savedInstanceState.getLong(key);
} else if (field.getType() == float.class) {
val = savedInstanceState.getFloat(key);
} else if (field.getType() == double.class) {
val = savedInstanceState.getDouble(key);
} else if (field.getType() == String.class) {
val = savedInstanceState.getString(key);
} else if (!isParcelableArray(field.getType()) && isSerializable(field.getType())) {
val = savedInstanceState.getSerializable(key);
} else if (isParcelable(field.getType())) {
val = savedInstanceState.getParcelable(key);
} else if (field.getType() == short[].class || field.getType() == Short[].class) {
val = savedInstanceState.getShortArray(key);
} else if (field.getType() == int[].class || field.getType() == Integer[].class) {
val = savedInstanceState.getIntArray(key);
} else if (field.getType() == long[].class || field.getType() == Long[].class) {
val = savedInstanceState.getLongArray(key);
} else if (field.getType() == float[].class || field.getType() == Float[].class) {
val = savedInstanceState.getFloatArray(key);
} else if (field.getType() == double[].class || field.getType() == Double[].class) {
val = savedInstanceState.getDoubleArray(key);
} else if (isParcelableArray(field.getType())) { //不支持Parcelable[]
// ArrayList<Parcelable> parcelableArrayList = savedInstanceState.getParcelableArrayList(key);
// Parcelable[] parcelables = parcelableArrayList.toArray(new Parcelable[]{});
// val = parcelables;
} else if (field.getType() == List.class || field.getType() == ArrayList.class) {
val = againListType(savedInstanceState, field, key);
} else {
throw new RuntimeException(activityOrFragment.getClass().getName() + ": 该类型不支持" +
field.getType().getName() +
", 支持的类型 包括基本类型，基本类型包装类，实现了Serializable，Parcelable接口对象，数组，一级List集合");
}
field.set(activityOrFragment, val);
}
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}
- 字段类型为 Fragment 类型 重新还原
public class ObjectInstanceManager {
/**
* 当app意外被杀死，重启后，重新实例化fragment
*
* @param fragmentManager activity 的 SupportFragmentManager， fragment 的 childFragmentManager
* @param activityOrFragment 必须是fragment或者activity
*/
public void againFragmentInstance(FragmentManager fragmentManager, Object activityOrFragment) {
if (fragmentManager.getFragments().size() <= 0) return;
//找出fragment 列表
List<Fragment> fragments = fragmentManager.getFragments();
//获取字段列表
Field[] declaredFields = activityOrFragment.getClass().getDeclaredFields();
if (declaredFields.length == 0) return;
for (Field field : declaredFields) {
if (field.isAnnotationPresent(AgainFragmentInstance.class)) {
AgainFragmentInstance annotation = field.getAnnotation(AgainFragmentInstance.class);
for (Fragment fragment : fragments) {
//注解中不带key，并且key不等于当前的tag 跳过
if (!TextUtils.isEmpty(annotation.tag())
&& !annotation.tag().equals(fragment.getTag())) {
continue;
}
//两种情况, 注解没有设置tag，那么直接判断字段类型的全类名和fragment列表中的fragment的全类名比较是否同一个。
//注解设置了tag，并且fragment的tag === 自定义注解的tag，那么再做上面的全类名比较
if (fragment.getClass().getName().equals(field.getType().getName())) {
field.setAccessible(true);
try {
field.set(activityOrFragment, fragment);
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}
}
}
}