鸿蒙HarmonyOS实战-ArkTS语言（渲染控制）_function return type inference ...

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正文

notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: string[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): string {
return this.dataArray[index];
}
public addData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: string): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
}
@Entry
@Component
struct MyComponent {
private data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(Hello ${i})
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: string) => {
ListItem() {
Row() {
Text(item).fontSize(50)
.onAppear(() => {
console.info(“appear:” + item)
})
}.margin({ left: 10, right: 10 })
}
}, (item: string) => ‘same key’)
}.cachedCount(5)
}
}
3.2.2 非初次渲染

3.2.2.1 添加数据

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: string[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): string {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: string[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): string {
return this.dataArray[index];
}
public addData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: string): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
}
@Entry
@Component
struct MyComponent {
private data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(Hello ${i})
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: string) => {
ListItem() {
Row() {
Text(item).fontSize(50)
.onAppear(() => {
console.info(“appear:” + item)
})
}.margin({ left: 10, right: 10 })
}
.onClick(() => {
// 点击追加子组件
this.data.pushData(Hello ${this.data.totalCount()});
})
}, (item: string) => item)
}.cachedCount(5)
}
}
3.2.2.2 删除数据

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: string[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): string {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
dataArray: string[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): string {
return this.dataArray[index];
}
public addData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: string): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
public deleteData(index: number): void {
this.dataArray.splice(index, 1);
this.notifyDataDelete(index);
}
}
@Entry
@Component
struct MyComponent {
private data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(Hello ${i})
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: string, index: number) => {
ListItem() {
Row() {
Text(item).fontSize(50)
.onAppear(() => {
console.info(“appear:” + item)
})
}.margin({ left: 10, right: 10 })
}
.onClick(() => {
// 点击删除子组件
this.data.deleteData(this.data.dataArray.indexOf(item));
})
}, (item: string) => item)
}.cachedCount(5)
}
}
3.2.2.3 改变单个数据

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: string[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): string {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: string[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): string {
return this.dataArray[index];
}
public addData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: string): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
public deleteData(index: number): void {
this.dataArray.splice(index, 1);
this.notifyDataDelete(index);
}
public changeData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataChange(index);
}
}
@Entry
@Component
struct MyComponent {
private moved: number[] = [];
private data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(Hello ${i})
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: string, index: number) => {
ListItem() {
Row() {
Text(item).fontSize(50)
.onAppear(() => {
console.info(“appear:” + item)
})
}.margin({ left: 10, right: 10 })
}
.onClick(() => {
this.data.changeData(index, item + ‘00’);
})
}, (item: string) => item)
}.cachedCount(5)
}
}
3.2.2.4 改变多个数据

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: string[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): string {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: string[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): string {
return this.dataArray[index];
}
public addData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: string): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
public deleteData(index: number): void {
this.dataArray.splice(index, 1);
this.notifyDataDelete(index);
}
public changeData(index: number): void {
this.notifyDataChange(index);
}
public reloadData(): void {
this.notifyDataReload();
}
public modifyAllData(): void {
this.dataArray = this.dataArray.map((item: string) => {
return item + ‘0’;
})
}
}
@Entry
@Component
struct MyComponent {
private moved: number[] = [];
private data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(Hello ${i})
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: string, index: number) => {
ListItem() {
Row() {
Text(item).fontSize(50)
.onAppear(() => {
console.info(“appear:” + item)
})
}.margin({ left: 10, right: 10 })
}
.onClick(() => {
this.data.modifyAllData();
this.data.reloadData();
})
}, (item: string) => item)
}.cachedCount(5)
}
}
3.2.2.5 改变数据子属性

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: StringData[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): StringData {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: StringData[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): StringData {
return this.dataArray[index];
}
public addData(index: number, data: StringData): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: StringData): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
}
@Observed
class StringData {
message: string;
constructor(message: string) {
this.message = message;
}
}
@Entry
@Component
struct MyComponent {
private moved: number[] = [];
@State data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(new StringData(Hello ${i}));
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: StringData, index: number) => {
ListItem() {
ChildComponent({data: item})
}
.onClick(() => {
item.message += ‘0’;
})
}, (item: StringData, index: number) => index.toString())
}.cachedCount(5)
}
}
@Component
struct ChildComponent {
@ObjectLink data: StringData
build() {
Row() {
Text(this.data.message).fontSize(50)
.onAppear(() => {
console.info(“appear:” + this.data.message)
})
}.margin({ left: 10, right: 10 })
}
}
3.2.3 问题点

3.2.3.1 索引重置

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: string[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): string {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: string[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): string {
return this.dataArray[index];
}
public addData(index: number, data: string): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: string): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
public deleteData(index: number): void {
this.dataArray.splice(index, 1);
this.notifyDataDelete(index);
}
public reloadData(): void {
this.notifyDataReload();
}
}
@Entry
@Component
struct MyComponent {
private data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(Hello ${i})
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: string, index: number) => {
ListItem() {
Row() {
Text(item).fontSize(50)
.onAppear(() => {
console.info(“appear:” + item)
})
}.margin({ left: 10, right: 10 })
}
.onClick(() => {
// 点击删除子组件
this.data.deleteData(index);
// 重置全部子组件的index索引
this.data.reloadData();
})
}, (item: string, index: number) => item + index.toString())
}.cachedCount(5)
}
}
3.2.3.2 图片闪耀

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: StringData[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): StringData {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: StringData[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): StringData {
return this.dataArray[index];
}
public addData(index: number, data: StringData): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: StringData): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
}
@Observed
class StringData {
message: string;
imgSrc: Resource;
constructor(message: string, imgSrc: Resource) {
this.message = message;
this.imgSrc = imgSrc;
}
}
@Entry
@Component
struct MyComponent {
@State data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(new StringData(Hello ${i}, $r(‘app.media.img’)));
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: StringData, index: number) => {
ListItem() {
ChildComponent({data: item})
}
.onClick(() => {
item.message += ‘0’;
})
}, (item: StringData, index: number) => index.toString())
}.cachedCount(5)
}
}
@Component
struct ChildComponent {
@ObjectLink data: StringData
build() {
Column() {
Text(this.data.message).fontSize(50)
.onAppear(() => {
console.info(“appear:” + this.data.message)
})
Image(this.data.imgSrc)
.width(500)
.height(200)
}.margin({ left: 10, right: 10 })
}
}
3.2.3.3 ObjectLink属性变化后UI更新

class BasicDataSource implements IDataSource {
private listeners: DataChangeListener[] = [];
private originDataArray: StringData[] = [];
public totalCount(): number {
return 0;
}
public getData(index: number): StringData {
return this.originDataArray[index];
}
registerDataChangeListener(listener: DataChangeListener): void {
if (this.listeners.indexOf(listener) < 0) {
console.info(‘add listener’);
this.listeners.push(listener);
}
}
unregisterDataChangeListener(listener: DataChangeListener): void {
const pos = this.listeners.indexOf(listener);
if (pos >= 0) {
console.info(‘remove listener’);
this.listeners.splice(pos, 1);
}
}
notifyDataReload(): void {
this.listeners.forEach(listener => {
listener.onDataReloaded();
})
}
notifyDataAdd(index: number): void {
this.listeners.forEach(listener => {
listener.onDataAdd(index);
})
}
notifyDataChange(index: number): void {
this.listeners.forEach(listener => {
listener.onDataChange(index);
})
}
notifyDataDelete(index: number): void {
this.listeners.forEach(listener => {
listener.onDataDelete(index);
})
}
}
class MyDataSource extends BasicDataSource {
private dataArray: StringData[] = [];
public totalCount(): number {
return this.dataArray.length;
}
public getData(index: number): StringData {
return this.dataArray[index];
}
public addData(index: number, data: StringData): void {
this.dataArray.splice(index, 0, data);
this.notifyDataAdd(index);
}
public pushData(data: StringData): void {
this.dataArray.push(data);
this.notifyDataAdd(this.dataArray.length - 1);
}
}
@Observed
class StringData {
message: NestedString;
constructor(message: NestedString) {
this.message = message;
}
}
@Observed
class NestedString {
message: string;
constructor(message: string) {
this.message = message;
}
}
@Entry
@Component
struct MyComponent {
private moved: number[] = [];
@State data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(new StringData(new NestedString(Hello ${i})));
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: StringData, index: number) => {
ListItem() {
ChildComponent({data: item})
}
.onClick(() => {
item.message = new NestedString(item.message.message + ‘0’);
})
}, (item: StringData, index: number) => item.toString() + index.toString())
}.cachedCount(5)
}
}
@Component
struct ChildComponent {
@ObjectLink data: StringData
网上学习资料一大堆，但假如学到的知识不成体系，遇到问题时只是浅尝辄止，不再深入研究，那么很难做到真正的技能提拔。
必要这份体系化的资料的朋友，可以添加V获取：vip204888 （备注鸿蒙）

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nstructor(message: NestedString) {
this.message = message;
}
}
@Observed
class NestedString {
message: string;
constructor(message: string) {
this.message = message;
}
}
@Entry
@Component
struct MyComponent {
private moved: number[] = [];
@State data: MyDataSource = new MyDataSource();
aboutToAppear() {
for (let i = 0; i <= 20; i++) {
this.data.pushData(new StringData(new NestedString(Hello ${i})));
}
}
build() {
List({ space: 3 }) {
LazyForEach(this.data, (item: StringData, index: number) => {
ListItem() {
ChildComponent({data: item})
}
.onClick(() => {
item.message = new NestedString(item.message.message + ‘0’);
})
}, (item: StringData, index: number) => item.toString() + index.toString())
}.cachedCount(5)
}
}
@Component
struct ChildComponent {
@ObjectLink data: StringData
网上学习资料一大堆，但假如学到的知识不成体系，遇到问题时只是浅尝辄止，不再深入研究，那么很难做到真正的技能提拔。
必要这份体系化的资料的朋友，可以添加V获取：vip204888 （备注鸿蒙）
[外链图片转存中…(img-1e9u0f8I-1713213699269)]
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