ボイラープレートを削減するために、以下を使用して、interfaceインスタンスの状態を保存classするために読み取り/書き込みを行います。Bundle
まず、インスタンス変数に注釈を付けるために使用されるインターフェースを作成します。
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({
ElementType.FIELD
})
public @interface SaveInstance {
}
次に、リフレクションを使用して値をバンドルに保存するクラスを作成します。
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import java.io.Serializable;
import java.lang.reflect.Field;
/**
* Save and load fields to/from a {@link Bundle}. All fields should be annotated with {@link
* SaveInstance}.</p>
*/
public class Icicle {
private static final String TAG = "Icicle";
/**
* Find all fields with the {@link SaveInstance} annotation and add them to the {@link Bundle}.
*
* @param outState
* The bundle from {@link Activity#onSaveInstanceState(Bundle)} or {@link
* Fragment#onSaveInstanceState(Bundle)}
* @param classInstance
* The object to access the fields which have the {@link SaveInstance} annotation.
* @see #load(Bundle, Object)
*/
public static void save(Bundle outState, Object classInstance) {
save(outState, classInstance, classInstance.getClass());
}
/**
* Find all fields with the {@link SaveInstance} annotation and add them to the {@link Bundle}.
*
* @param outState
* The bundle from {@link Activity#onSaveInstanceState(Bundle)} or {@link
* Fragment#onSaveInstanceState(Bundle)}
* @param classInstance
* The object to access the fields which have the {@link SaveInstance} annotation.
* @param baseClass
* Base class, used to get all superclasses of the instance.
* @see #load(Bundle, Object, Class)
*/
public static void save(Bundle outState, Object classInstance, Class<?> baseClass) {
if (outState == null) {
return;
}
Class<?> clazz = classInstance.getClass();
while (baseClass.isAssignableFrom(clazz)) {
String className = clazz.getName();
for (Field field : clazz.getDeclaredFields()) {
if (field.isAnnotationPresent(SaveInstance.class)) {
field.setAccessible(true);
String key = className + "#" + field.getName();
try {
Object value = field.get(classInstance);
if (value instanceof Parcelable) {
outState.putParcelable(key, (Parcelable) value);
} else if (value instanceof Serializable) {
outState.putSerializable(key, (Serializable) value);
}
} catch (Throwable t) {
Log.d(TAG, "The field '" + key + "' was not added to the bundle");
}
}
}
clazz = clazz.getSuperclass();
}
}
/**
* Load all saved fields that have the {@link SaveInstance} annotation.
*
* @param savedInstanceState
* The saved-instance {@link Bundle} from an {@link Activity} or {@link Fragment}.
* @param classInstance
* The object to access the fields which have the {@link SaveInstance} annotation.
* @see #save(Bundle, Object)
*/
public static void load(Bundle savedInstanceState, Object classInstance) {
load(savedInstanceState, classInstance, classInstance.getClass());
}
/**
* Load all saved fields that have the {@link SaveInstance} annotation.
*
* @param savedInstanceState
* The saved-instance {@link Bundle} from an {@link Activity} or {@link Fragment}.
* @param classInstance
* The object to access the fields which have the {@link SaveInstance} annotation.
* @param baseClass
* Base class, used to get all superclasses of the instance.
* @see #save(Bundle, Object, Class)
*/
public static void load(Bundle savedInstanceState, Object classInstance, Class<?> baseClass) {
if (savedInstanceState == null) {
return;
}
Class<?> clazz = classInstance.getClass();
while (baseClass.isAssignableFrom(clazz)) {
String className = clazz.getName();
for (Field field : clazz.getDeclaredFields()) {
if (field.isAnnotationPresent(SaveInstance.class)) {
String key = className + "#" + field.getName();
field.setAccessible(true);
try {
Object fieldVal = savedInstanceState.get(key);
if (fieldVal != null) {
field.set(classInstance, fieldVal);
}
} catch (Throwable t) {
Log.d(TAG, "The field '" + key + "' was not retrieved from the bundle");
}
}
}
clazz = clazz.getSuperclass();
}
}
}
使用例:
public class MainActivity extends Activity {
@SaveInstance
private String foo;
@SaveInstance
private int bar;
@SaveInstance
private Intent baz;
@SaveInstance
private boolean qux;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Icicle.load(savedInstanceState, this);
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Icicle.save(outState, this);
}
}
注:このコードは、 MITライセンスの下でライセンスされているAndroidAutowireという名前のライブラリ プロジェクトから改作されました。