本实验主要涉及的知识点是数据库的创建和数据库的增、删、查、改。Android系统推荐创建数据库的方法，是创建自己的继承自SQLiteOpenHelper类的子类，并重写其中的两个抽象方法onCreate（）和onUpdate（），然后分别在这两个方法中去实现创建、升级数据库的逻辑。
除了上面提到的两个抽象的方法外，SQLiteOpenHelper中还有两个非常重要的实例方法：getReadableDatabase（）和getWriteableDatabase（），SQLiteOpenHelper的子类通过这两个方法来获取SQlite数据库的实例对象，并保证以同步的方式访问。通常情况下getReadableDatabase（）和getWriteableDatabase（）方法都是创建或者打开一个现有的数据库，并返回一个对数据库进行读写操作的对象。但是在某些情况下，例如磁盘已经满的情况下，getReadableDatabase（）方法返回的对象将只以读的方式打开数据库，而getWriteableDatabase（）方法将抛出异常。
资源文件列表
MyContactBook/.gitignore , 216
MyContactBook/.gradle/4.10.1/fileChanges/last-build.bin , 1
MyContactBook/.gradle/4.10.1/fileContent/fileContent.lock , 17
MyContactBook/.gradle/4.10.1/fileHashes/fileHashes.bin , 131133
MyContactBook/.gradle/4.10.1/fileHashes/fileHashes.lock , 17
MyContactBook/.gradle/4.10.1/fileHashes/resourceHashesCache.bin , 18565
MyContactBook/.gradle/4.10.1/gc.properties , 0
MyContactBook/.gradle/4.10.1/javaCompile/classAnalysis.bin , 107531
MyContactBook/.gradle/4.10.1/javaCompile/javaCompile.lock , 17
MyContactBook/.gradle/4.10.1/javaCompile/taskHistory.bin , 23746
MyContactBook/.gradle/4.10.1/taskHistory/taskHistory.bin , 1312897
MyContactBook/.gradle/4.10.1/taskHistory/taskHistory.lock , 17
MyContactBook/.gradle/buildOutputCleanup/buildOutputCleanup.lock , 17
MyContactBook/.gradle/buildOutputCleanup/cache.properties , 54
MyContactBook/.gradle/buildOutputCleanup/outputFiles.bin , 20945
MyContactBook/.gradle/vcs-1/gc.properties , 0
MyContactBook/.idea/caches/build_file_checksums.ser , 545
MyContactBook/.idea/caches/gradle_models.ser , 145230
MyContactBook/.idea/codeStyles/Project.xml , 1803
MyContactBook/.idea/gradle.xml , 594
MyContactBook/.idea/libraries/Gradle__android_arch_core_common_1_1_1_jar.xml , 541
MyContactBook/.idea/libraries/Gradle__android_arch_core_runtime_1_1_1_aar.xml , 659
MyContactBook/.idea/libraries/Gradle__android_arch_lifecycle_common_1_1_1_jar.xml , 556
MyContactBook/.idea/libraries/Gradle__android_arch_lifecycle_livedata_1_1_1_aar.xml , 675
MyContactBook/.idea/libraries/Gradle__android_arch_lifecycle_livedata_core_1_1_1_aar.xml , 699
MyContactBook/.idea/libraries/Gradle__android_arch_lifecycle_runtime_1_1_1_aar.xml , 670
MyContactBook/.idea/libraries/Gradle__android_arch_lifecycle_viewmodel_1_1_1_aar.xml , 680
MyContactBook/.idea/libraries/Gradle__com_android_support_animated_vector_drawable_28_0_0_aar.xml , 526
MyContactBook/.idea/libraries/Gradle__com_android_support_appcompat_v7_28_0_0_aar.xml , 682
MyContactBook/.idea/libraries/Gradle__com_android_support_asynclayoutinflater_28_0_0_aar.xml , 511
MyContactBook/.idea/libraries/Gradle__com_android_support_collections_28_0_0_jar.xml , 375
MyContactBook/.idea/libraries/Gradle__com_android_support_constraint_constraint_layout_1_1_3_aar.xml , 513
MyContactBook/.idea/libraries/Gradle__com_android_support_constraint_constraint_layout_solver_1_1_3_jar.xml , 433
MyContactBook/.idea/libraries/Gradle__com_android_support_coordinatorlayout_28_0_0_aar.xml , 702
MyContactBook/.idea/libraries/Gradle__com_android_support_cursoradapter_28_0_0_aar.xml , 493
MyContactBook/.idea/libraries/Gradle__com_android_support_customview_28_0_0_aar.xml , 484
MyContactBook/.idea/libraries/Gradle__com_android_support_documentfile_28_0_0_aar.xml , 490
MyContactBook/.idea/libraries/Gradle__com_android_support_drawerlayout_28_0_0_aar.xml , 682
MyContactBook/.idea/libraries/Gradle__com_android_support_interpolator_28_0_0_aar.xml , 490
MyContactBook/.idea/libraries/Gradle__com_android_support_loader_28_0_0_aar.xml , 472
MyContactBook/.idea/libraries/Gradle__com_android_support_localbroadcastmanager_28_0_0_aar.xml , 517
MyContactBook/.idea/libraries/Gradle__com_android_support_print_28_0_0_aar.xml , 654
MyContactBook/.idea/libraries/Gradle__com_android_support_slidingpanelayout_28_0_0_aar.xml , 505
MyContactBook/.idea/libraries/Gradle__com_android_support_support_annotations_28_0_0_jar.xml , 399
MyContactBook/.idea/libraries/Gradle__com_android_support_support_compat_28_0_0_aar.xml , 690
MyContactBook/.idea/libraries/Gradle__com_android_support_support_core_ui_28_0_0_aar.xml , 499
MyContactBook/.idea/libraries/Gradle__com_android_support_support_core_utils_28_0_0_aar.xml , 508
MyContactBook/.idea/libraries/Gradle__com_android_support_support_fragment_28_0_0_aar.xml , 698
MyContactBook/.idea/libraries/Gradle__com_android_support_support_vector_drawable_28_0_0_aar.xml , 523
MyContactBook/.idea/libraries/Gradle__com_android_support_swiperefreshlayout_28_0_0_aar.xml , 706
MyContactBook/.idea/libraries/Gradle__com_android_support_test_espresso_espresso_core_3_0_2_aar.xml , 722
MyContactBook/.idea/libraries/Gradle__com_android_support_test_espresso_espresso_idling_resource_3_0_2_aar.xml , 777
MyContactBook/.idea/libraries/Gradle__com_android_support_test_monitor_1_0_2_aar.xml , 674
MyContactBook/.idea/libraries/Gradle__com_android_support_test_runner_1_0_2_aar.xml , 669
MyContactBook/.idea/libraries/Gradle__com_android_support_versionedparcelable_28_0_0_aar.xml , 511
MyContactBook/.idea/libraries/Gradle__com_android_support_viewpager_28_0_0_aar.xml , 481
MyContactBook/.idea/libraries/Gradle__com_google_code_findbugs_jsr305_2_0_1_jar.xml , 367
MyContactBook/.idea/libraries/Gradle__com_squareup_javawriter_2_1_1_jar.xml , 546
MyContactBook/.idea/libraries/Gradle__javax_inject_javax_inject_1_jar.xml , 536
MyContactBook/.idea/libraries/Gradle__junit_junit_4_12_jar.xml , 495
MyContactBook/.idea/libraries/Gradle__net_sf_kxml_kxml2_2_3_0_jar.xml , 518
MyContactBook/.idea/libraries/Gradle__org_hamcrest_hamcrest_core_1_3_jar.xml , 551
MyContactBook/.idea/libraries/Gradle__org_hamcrest_hamcrest_integration_1_3_jar.xml , 586
MyContactBook/.idea/libraries/Gradle__org_hamcrest_hamcrest_library_1_3_jar.xml , 565
MyContactBook/.idea/misc.xml , 365
MyContactBook/.idea/modules.xml , 371
MyContactBook/.idea/runConfigurations.xml , 575
MyContactBook/.idea/workspace.xml , 15581
MyContactBook/app/.gitignore , 8
MyContactBook/app/app.iml , 15184
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/arch/core/R.java , 269
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/arch/lifecycle/livedata/core/R.java , 288
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/arch/lifecycle/livedata/R.java , 283
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/arch/lifecycle/R.java , 274
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/arch/lifecycle/viewmodel/R.java , 284
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/asynclayoutinflater/R.java , 10649
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/compat/R.java , 10636
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/constraint/R.java , 19449
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/coordinatorlayout/R.java , 12617
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/coreui/R.java , 12606
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/coreutils/R.java , 10639
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/cursoradapter/R.java , 281
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/customview/R.java , 10640
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/documentfile/R.java , 280
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/drawerlayout/R.java , 10642
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/fragment/R.java , 12608
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/graphics/drawable/R.java , 12617
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/interpolator/R.java , 280
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/loader/R.java , 10636
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/localbroadcastmanager/R.java , 289
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/print/R.java , 273
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/slidingpanelayout/R.java , 10647
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/swiperefreshlayout/R.java , 10648
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/v7/appcompat/R.java , 122451
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/android/support/v7/viewpager/R.java , 10642
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/androidx/versionedparcelable/R.java , 280
MyContactBook/app/build/generated/not_namespaced_r_class_sources/debug/processDebugResources/r/com/example/mycontactbook/R.java , 684060
MyContactBook/app/build/generated/res/pngs/debug/drawable-anydpi-v21/ic_launcher_background.xml , 5776
MyContactBook/app/build/generated/res/pngs/debug/drawable-hdpi/ic_launcher_background.png , 837
MyContactBook/app/build/generated/res/pngs/debug/drawable-ldpi/ic_launcher_background.png , 339
MyContactBook/app/build/generated/res/pngs/debug/drawable-mdpi/ic_launcher_background.png , 411
MyContactBook/app/build/generated/res/pngs/debug/drawable-xhdpi/ic_launcher_background.png , 1255
MyContactBook/app/build/generated/res/pngs/debug/drawable-xxhdpi/ic_launcher_background.png , 2881
MyContactBook/app/build/generated/res/pngs/debug/drawable-xxxhdpi/ic_launcher_background.png , 4759
MyContactBook/app/build/generated/source/buildConfig/debug/com/example/mycontactbook/BuildConfig.java , 457
MyContactBook/app/build/intermediates/annotation_processor_list/debug/annotationProcessors.json , 2
MyContactBook/app/build/intermediates/apk_list/debug/mainApkListPersistenceDebug/apk-list.gson , 147
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/debug.json , 231682
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-af.json , 2002
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-am.json , 2000
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-ar.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-as.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-az.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-b+sr+Latn.json , 2048
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-be.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-bg.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-bn.json , 2007
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-bs.json , 2006
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-ca.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-cs.json , 2003
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-da.json , 2001
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-de.json , 2006
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-el.json , 2007
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-en-rAU.json , 2026
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-en-rCA.json , 2026
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-en-rGB.json , 2026
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-en-rIN.json , 2026
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-en-rXC.json , 2054
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-es-rUS.json , 2029
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-es.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-et.json , 2008
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-eu.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-fa.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-fi.json , 2001
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-fr-rCA.json , 2031
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-fr.json , 2007
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-gl.json , 2006
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-gu.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-h720dp-v13.json , 779
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-hdpi-v4.json , 808
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-hi.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-hr.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-hu.json , 2006
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-hy.json , 2003
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-in.json , 2005
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-is.json , 2001
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-it.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-iw.json , 2001
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-ja.json , 1998
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-ka.json , 2004
MyContactBook/app/build/intermediates/blame/res/debug/multi-v2/values-kk.json , 2003
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