android.os.TransactionTooLargeException: data parcel size 4195216 bytes问题原因与解决

从AActivity跳转BActivity通过intent.putExtra传递数据，结果报android.os.TransactionTooLargeException: data parcel size 4195216 bytes错误，意思就是传输的数据过大，4195216byte转换下大概为4Mb，确实有点大，因为是从本地文件读取的String内容，可能文件内容太大。

源码

遇到问题我们首先看下TransactionTooLargeException这个类的源码注释，里面肯定有说明

通过以下源码注释内容可以了解到以下几点信息：

• 通过Intent传递或者返回的数据是存放在一个叫做Binder transaction buffer的缓存区，这个缓冲区的大小为1Mb(Android 28 Platform)，当缓冲区不够用时就会抛出异常
• 如果有多个数据传递同时进行，是共用缓冲区的1Mb，而不是每一个传输各分配1Mb缓存。这就有可能当多个传输同时进行时，数据大小小于1M还是抛出TransactionTooLargeException异常
• 建议的解决方法就是尽可能减小传输的数据，至于具体要多效合上也没个具体的数值，也不可能知道，因为并发传输的数量不固定，但是至少可以肯定的是超过1M肯定会抛异常

/**
 * The Binder transaction failed because it was too large.
 * <p>
 * During a remote procedure call, the arguments and the return value of the call
 * are transferred as {@link Parcel} objects stored in the Binder transaction buffer.
 * If the arguments or the return value are too large to fit in the transaction buffer,
 * then the call will fail and {@link TransactionTooLargeException} will be thrown.
 * </p><p>
 * The Binder transaction buffer has a limited fixed size, currently 1Mb, which
 * is shared by all transactions in progress for the process.  Consequently this
 * exception can be thrown when there are many transactions in progress even when
 * most of the individual transactions are of moderate size.
 * </p><p>
 * There are two possible outcomes when a remote procedure call throws
 * {@link TransactionTooLargeException}.  Either the client was unable to send
 * its request to the service (most likely if the arguments were too large to fit in
 * the transaction buffer), or the service was unable to send its response back
 * to the client (most likely if the return value was too large to fit
 * in the transaction buffer).  It is not possible to tell which of these outcomes
 * actually occurred.  The client should assume that a partial failure occurred.
 * </p><p>
 * The key to avoiding {@link TransactionTooLargeException} is to keep all
 * transactions relatively small.  Try to minimize the amount of memory needed to create
 * a {@link Parcel} for the arguments and the return value of the remote procedure call.
 * Avoid transferring huge arrays of strings or large bitmaps.
 * If possible, try to break up big requests into smaller pieces.
 * </p><p>
 * If you are implementing a service, it may help to impose size or complexity
 * contraints on the queries that clients can perform.  For example, if the result set
 * could become large, then don't allow the client to request more than a few records
 * at a time.  Alternately, instead of returning all of the available data all at once,
 * return the essential information first and make the client ask for additional information
 * later as needed.
 * </p>
 */
public class TransactionTooLargeException extends RemoteException {
    public TransactionTooLargeException() {
        super();
    }

    public TransactionTooLargeException(String msg) {
        super(msg);
    }
}

解决方法

根据官方的建议就是减小传输的数据大小，或者拆分数据分次传输，但是如果数据量真的很大且需一次性传输有没解决方法呢，当然有

1. 数据保存到static全局变量中
2. 数据保存到本地存储中，比如本地文件或数据库，在目标Activity中再提取出来
3. 通过EventBus.postSticky传递包含传递数据的粘性事件，在目标Activity中接收该事件提取数据(关于粘性事件参考Android EventBus Sticky Events粘性事件详解)