Android：ContentProvider总结
2019-03-24 本文已影响0人
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如何使用contentprovider？
1.新建一个类继承于ContentProvider。
public class BedWatchingProvider extends ContentProvider
2.在AndroidManifest中定义她，并且定义他的authorities
<provider
android:name=".BedWatchingProvider"
android:authorities="com.wenfengtou.bedwatching.bedwatchingprovider"
android:enabled="true"
android:exported="true"></provider>
3.新建一个数据库帮助类
private static class DatabaseOpenHelper extends SQLiteOpenHelper
4.定义Uri匹配
匹配bedwatching table
sMatcher.addURI(AUTHORITY, "bedwatching", URI_Bed_Watching);
5.在客户端使用contentResolver去获取
ContentResolver contentResolver = MainActivity.this.getContentResolver();
Uri uri = new Uri.Builder().scheme(ContentResolver.SCHEME_CONTENT).authority("com.wenfengtou.bedwatching.bedwatchingprovider")
.appendPath("bedwatching").build();
Cursor cursor = contentResolver.query(uri,null,null,null,null);
if (cursor.moveToFirst()) {
Log.i(TAG,"print " + cursor.getColumnIndex("name") + " " + cursor.getString(cursor.getColumnIndex("name")));
}
android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1 怎么解决？
获取到数据库的Cursor后，需要首先移动一个游标。
参考：https://blog.csdn.net/woshixuye/article/details/8260547
https://blog.csdn.net/niuba123456/article/details/42638285
QLiteDatabase: android.database.sqlite.SQLiteConstraintException: UNIQUE constraint failed 怎么解决？
是因为重复写数据导致的。我的代码定义了INTEGER PRIMARY KEY AUTOINCREMENT。这个是主键，主键不能重复先的。例如0写了，不能再次直接写入0。
参考：https://blog.csdn.net/wwzqj/article/details/7801702
FileProvider与ContentProvider的区别？
ContentProvider启动流程
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at com.wenfengtou.bedwatching.BedWatchingProvider.onCreate(BedWatchingProvider.java:58)
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at android.content.ContentProvider.attachInfo(ContentProvider.java:1748)
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at android.content.ContentProvider.attachInfo(ContentProvider.java:1723)
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at android.app.ActivityThread.installProvider(ActivityThread.java:5153)
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at android.app.ActivityThread.installContentProviders(ActivityThread.java:4748)
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4688)
03-29 23:32:30.629 3485 3485 I BedWatchingProvider: at android.app.ActivityThread.-wrap1(ActivityThread.java)
publishContentProviders做了什么？
在system_server进程生成一个hash变量mProviderMap，key是authority，value是ContentProviderRecord
ContentResolver查找流程？
确认与AMS进行binder通信的实体先，首先我们可以确认客户端和服务端的接口都是IContentProvider,这个类定义了客户端和服务端通用的接口，其实我们看哪个类继承与IInterface，就知道它是一个binder接口。
public interface IContentProvider extends IInterface {
public Cursor query(String callingPkg, Uri url, String[] projection, String selection,
String[] selectionArgs, String sortOrder, ICancellationSignal cancellationSignal)
throws RemoteException;
public String getType(Uri url) throws RemoteException;
public Uri insert(String callingPkg, Uri url, ContentValues initialValues)
throws RemoteException;
public int bulkInsert(String callingPkg, Uri url, ContentValues[] initialValues)
throws RemoteException;
public int delete(String callingPkg, Uri url, String selection, String[] selectionArgs)
throws RemoteException;
public int update(String callingPkg, Uri url, ContentValues values, String selection,
String[] selectionArgs) throws RemoteException;
public ParcelFileDescriptor openFile(
String callingPkg, Uri url, String mode, ICancellationSignal signal,
IBinder callerToken)
throws RemoteException, FileNotFoundException;
public AssetFileDescriptor openAssetFile(
String callingPkg, Uri url, String mode, ICancellationSignal signal)
throws RemoteException, FileNotFoundException;
public ContentProviderResult[] applyBatch(String callingPkg,
ArrayList<ContentProviderOperation> operations)
throws RemoteException, OperationApplicationException;
public Bundle call(
String callingPkg, String method, @Nullable String arg, @Nullable Bundle extras)
throws RemoteException;
public ICancellationSignal createCancellationSignal() throws RemoteException;
public Uri canonicalize(String callingPkg, Uri uri) throws RemoteException;
public Uri uncanonicalize(String callingPkg, Uri uri) throws RemoteException;
// Data interchange.
public String[] getStreamTypes(Uri url, String mimeTypeFilter) throws RemoteException;
public AssetFileDescriptor openTypedAssetFile(String callingPkg, Uri url, String mimeType,
Bundle opts, ICancellationSignal signal) throws RemoteException, FileNotFoundException;
/* IPC constants */
static final String descriptor = "android.content.IContentProvider";
static final int QUERY_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION;
static final int GET_TYPE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 1;
static final int INSERT_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 2;
static final int DELETE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 3;
static final int UPDATE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 9;
static final int BULK_INSERT_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 12;
static final int OPEN_FILE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 13;
static final int OPEN_ASSET_FILE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 14;
static final int APPLY_BATCH_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 19;
static final int CALL_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 20;
static final int GET_STREAM_TYPES_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 21;
static final int OPEN_TYPED_ASSET_FILE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 22;
static final int CREATE_CANCELATION_SIGNAL_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 23;
static final int CANONICALIZE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 24;
static final int UNCANONICALIZE_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION + 25;
}
谁实现这个接口就是binder实体,所以ContentProviderNative就是binder实体，但是它是抽象的，所以不能实例化，肯定有一个类继承与它，作为最终的binder实体。
abstract public class ContentProviderNative extends Binder implements IContentProvider {
这个 最终的类就是Transport,为什么要中间搞一个抽象类呢？是类Transport还扩充了额外的功能，例如权限限制等。
class Transport extends ContentProviderNative {
ContentProvider如何自定义权限？
在AndroidManifest中定义
<permission android:name="com.wenfengtou.bedwatching.permission.READ_PROVIDER"
android:protectionLevel="normal" />
<provider
android:name=".BedWatchingProvider"
android:authorities="com.wenfengtou.bedwatching.bedwatchingprovider"
android:enabled="true"
android:exported="true"
android:permission="com.wenfengtou.bedwatching.permission.READ_PROVIDER"></provider>
如何获取contentprovider的应用没有申请这个权限就会报错
03-31 20:58:05.226 8733 8733 E AndroidRuntime: Caused by: java.lang.SecurityException: Permission Denial: opening provider com.wenfengtou.bedwatching.BedWatchingProvider from ProcessRecord{bda6cd8 8733:com.example.wenfengtou.myapplication/u0a60} (pid=8733, uid=10060) requires com.wenfengtou.bedwatching.permission.READ_PROVIDER or com.wenfengtou.bedwatching.permission.READ_PROVIDER
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.os.Parcel.readException(Parcel.java:1599)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.os.Parcel.readException(Parcel.java:1552)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.app.ActivityManagerProxy.getContentProvider(ActivityManagerNative.java:3550)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.app.ActivityThread.acquireProvider(ActivityThread.java:4778)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.app.ContextImpl$ApplicationContentResolver.acquireUnstableProvider(ContextImpl.java:2018)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.content.ContentResolver.acquireUnstableProvider(ContentResolver.java:1468)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.content.ContentResolver.query(ContentResolver.java:475)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.content.ContentResolver.query(ContentResolver.java:434)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at com.example.wenfengtou.myapplication.MainActivity.onResume(MainActivity.java:34)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1258)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.app.Activity.performResume(Activity.java:6312)
03-31 20:58:05.226 8733 8733 E AndroidRuntime: at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3092)
这个定位源码是在AMS中函数
getContentProviderImpl － checkContentProviderPermissionLocked
除了这个地方拦截权限，还有另一个地方
/frameworks/base/core/java/android/content/ContentProvider.java
enforceReadPermissionInner
这个函数是跑在ContentProvider进程中的。
ContentProvider的数据是如何传递的？
public interface IBulkCursor extends IInterface
public final class CursorToBulkCursorAdaptor extends BulkCursorNative
/frameworks/base/core/java/android/content/ContentProviderNative.java
case QUERY_TRANSACTION:
{
data.enforceInterface(IContentProvider.descriptor);
String callingPkg = data.readString();
Uri url = Uri.CREATOR.createFromParcel(data);
// String[] projection
int num = data.readInt();
String[] projection = null;
if (num > 0) {
projection = new String[num];
for (int i = 0; i < num; i++) {
projection[i] = data.readString();
}
}
Bundle queryArgs = data.readBundle();
IContentObserver observer = IContentObserver.Stub.asInterface(
data.readStrongBinder());
ICancellationSignal cancellationSignal = ICancellationSignal.Stub.asInterface(
data.readStrongBinder());
Cursor cursor = query(callingPkg, url, projection, queryArgs, cancellationSignal);
if (cursor != null) {
CursorToBulkCursorAdaptor adaptor = null;
try {
adaptor = new CursorToBulkCursorAdaptor(cursor, observer,
getProviderName());
cursor = null;
BulkCursorDescriptor d = adaptor.getBulkCursorDescriptor();
adaptor = null;
reply.writeNoException();
reply.writeInt(1);
d.writeToParcel(reply, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
} finally {
// Close cursor if an exception was thrown while constructing the adaptor.
if (adaptor != null) {
adaptor.close();
}
if (cursor != null) {
cursor.close();
}
}
} else {
reply.writeNoException();
reply.writeInt(0);
}
return true;
}
创建共享内存的代码如下
/frameworks/base/libs/androidfw/CursorWindow.cpp
CursorWindow::CursorWindow(const String8& name, int ashmemFd,
void* data, size_t size, bool readOnly) :
mName(name), mAshmemFd(ashmemFd), mData(data), mSize(size), mReadOnly(readOnly) {
mHeader = static_cast<Header*>(mData);
}
status_t CursorWindow::create(const String8& name, size_t size, CursorWindow** outCursorWindow) {
String8 ashmemName("CursorWindow: ");
ashmemName.append(name);
status_t result;
int ashmemFd = ashmem_create_region(ashmemName.string(), size); //这里创建了共享内存
if (ashmemFd < 0) {
result = -errno;
} else {
result = ashmem_set_prot_region(ashmemFd, PROT_READ | PROT_WRITE);
if (result >= 0) {
void* data = ::mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, ashmemFd, 0);
if (data == MAP_FAILED) {
result = -errno;
} else {
result = ashmem_set_prot_region(ashmemFd, PROT_READ);
if (result >= 0) {
CursorWindow* window = new CursorWindow(name, ashmemFd,
data, size, false /*readOnly*/);
result = window->clear();
if (!result) {
LOG_WINDOW("Created new CursorWindow: freeOffset=%d, "
"numRows=%d, numColumns=%d, mSize=%d, mData=%p",
window->mHeader->freeOffset,
window->mHeader->numRows,
window->mHeader->numColumns,
window->mSize, window->mData);
*outCursorWindow = window;
return OK;
}
delete window;
}
}
::munmap(data, size);
}
::close(ashmemFd);
}
*outCursorWindow = NULL;
return result;
}
参考：https://blog.csdn.net/new_abc/article/details/8167973
ContentProvider的权限怎么控制？
1.设置android:readPermission，设置android:writePermission
2.设置path-permission，注意android:readPermission的优先级高于path-permission，即如果客户端已经有android:readPermission的权限，则不检验path-permission。如果不满足android:readPermission的权限，则会再看path-permission是否满足。
参考
http://androidxref.com/6.0.0_r1/xref/packages/providers/DownloadProvider/AndroidManifest.xml#72
checkHoldingPermissionsLocked这个对于uri临时授权关键。
ams检查是用checkUriPermission
FileProvider是什么？
FileProvider继承与ContentProvider，用Content：//代替原来的file：//。
