How does Buddhism explain the generation principle of dreams?

Buddhism holds a positive attitude towards dreams, and Buddhism has occupied dreams many times. Dreams in Buddhist scriptures are mainly about strange dreams that indicate important events. The interpretation of symptomatic dreams mainly adopts the interpretation method of direct symbols. For example, Ananda's Seven Dreams tells that Ananda, a Buddhist waiter, had seven nightmares at night. After waking up, he recalled that he was "very scared" and told the Buddha that the dream was about to be set, and he walked on Mount Sumeru, indicating that the Buddha was going to die. Ananda will take on the important task of telling Buddhist scriptures to his disciples after the death of Buddha. The fire of dream water indicates that many monks will go against the teachings of Buddha in the future to win support; The dream pig came out of the cesspit and knocked down the sandalwood tree, which indicated that his family would not obey the Buddhist precepts, drink confused and slander arhat in the future; There are insects eating the lion's flesh in the dream lion, which indicates that there will be no heretics to destroy Buddhism in the future, and only Buddhist disciples can destroy Buddhism: Download the Karma Sutra of Lonely Old Women, and Buddha said: The ten dreams of King Li Ji from the past to the present explained by Kaye Buddha all indicate the future. For example, you dream that an elephant came out of the window. Although its body was painted, its tail was blocked by the window, which indicates that Sakyamuni Buddha will die in the future. I dreamed that there was a piece of white cotton cloth, and eighteen people fought over it, but the cloth could not be torn, which indicated that after the death of Sakyamuni Buddha in the future, the disciples of the Buddha split into eighteen factions. This explanation is not so much a dream as a way to teach disciples and warn future generations. Fifty years after the publication of Add Agama, the Persian king of slava had ten nightmares. After waking up, he was "very worried and afraid of national subjugation" and gathered ministers, ministers, brahmins, etc. Another Brahmin priest interpreted it as a sign of the death of the king, prince and wife, saying that only killing the prince and princess could solve him. The king of Persia listened to his wife's advice and asked the Buddha for advice. The Buddha said that his dream was not evil, but the response of future generations. Like a dream with three pots listed, the two sides were full, the middle pot was empty, and the boiling gas on both sides intersected without entering the middle pot, indicating that future generations would not support their loved ones, but would be close to wealth, and would reciprocate and give gifts to each other. People who dream that horses eat grass at their mouths and horses eat grass at their buttocks indicate that ministers and officials in later generations will not only eat state salaries, but also exploit ordinary people. "People won't feel peaceful and uneasy about this ancient land." Dream Black Bull came from all directions, growling to fight. If it didn't, it boded ill for future kings, officials and people. "Lust for lust, store property, unclean wife and daughter, gluttony, jealousy, shame, disloyalty and flattery to the country." Dreaming that the water in the center is turbid and the water around is clear shows that the ministers here are disloyal, unfilial, disrespectful to their elders, don't believe in Buddhism, and don't pay attention to etiquette and benevolence, while the surrounding ministers are loyal to their sons and filial sons, respect their elders and believe in Buddhism. People who dream that the river of Daxi is red indicate that the emperors of later generations will mobilize their troops and attack each other, causing rivers of blood.