phonegap: local storage
TRANSCRIPT
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localStorage
window.localStorage.setItem(“name”, “Ivano”);
var name = window.localStorage.getItem(“name”);
.key(0)
.getItem(“key”)
.setItem(“key”, “value”)
.removeItem(“key”)
.clear()
// simple class declaration
function Person(name, surname) {
this.name = name;
this.surname = surname;
}
// object creation
var user = new Person(„Ivano‟, „Malavolta‟);
// object serialization
window.localStorage.setItem(“user”, JSON.stringify(user));
// object retrieval
var current = JSON.parse(window.localStorage.getItem(“user”));
if (window.localStorage.getItem(“user”)) {
// there is an object in user
} else {
// the user key does not have any value
}
var users = [...]; // array of Person objects
window.localStorage.setItem(“users”,
JSON.stringify(users));
var allUsers =
JSON.parse(window.localStorage.getItem(“users”));
var ivanos = [];
for(var i=0; i<allUsers.length; i++) {
if(allUsers[i].name == „Ivano‟)
ivanos.push(allUsers[i]);
}
var usersNumber =
JSON.parse(window.localStorage.getItem(“users“)).length;
tx.executeSql("SELECT * FROM User“, [],
function(tx, result) {
// callback code
});
var db =
openDatabase(„Test', „1.0', „Test DB', 100000);
openDatabase(name, version, displayname, size);
db.changeVersion("1.0", "1.1");
db.transaction(queries, error, success);
function populateDB(tx) {
tx.executeSql('DROP TABLE IF EXISTS USER');
tx.executeSql('CREATE TABLE IF NOT EXISTS USER (id
unique, name, surname)');
tx.executeSql('INSERT INTO USER(id, name, surname)
VALUES (1, ?, ?)„, [“Ivano“, “Malavolta“],
success, error);
}
rows
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tx.executeSql('INSERT INTO USER(id, name,surname) VALUES (5,
?, ?)„, [“Ivano“, “Malavolta“], success, error);
}
function success(tx, results) {
var affected = results.rowsAffected(); // 1
}
function error(err) {
// code for managing the error
}
length
item(index)
...
tx.executeSql(„SELECT * FROM USER„, [], success, error);
}
function success(tx, results) {
var size = results.rows.length;
for (var i=0; i<size; i++){
console.log(results.rows.item(i).name);
}
}
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tx.executeSql(„SELECT * FROM USER„,[], success, error);
}
function error(err) {
console.log(err.code);
}
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requestFileSystem(type, size, successCb, [errorCb])
window.requestFileSystem(
LocalFileSystem.PERSISTENT,
0,
onSuccess,
onError);
function onSuccess(fileSystem) {
console.log(fileSystem.name);
}
window.resolveLocalFileSystemURI(
"file:///userImg.png", onSuccess, onError);
function onSuccess(fileEntry) {
console.log(fileEntry.name);
}
The real objects
Descriptor
Writing & Reading objects
entry.file(win, fail);
function win(file) {
var reader = new FileReader();
reader.onloadend = function(evt) {
console.log(evt.target.result);
};
reader.readAsText(file);
// reader.abort();
};
function fail(evt) {
console.log(error.code);
};
append
entry.createWriter(win, fail);
function win(writer) {
writer.onwrite = function(evt) {
console.log(“ok");
};
writer.write(“Ivano Malavolta");
};
function fail(evt) {
// error management
};
var directoryReader = dirEntry.createReader();
directoryReader.readEntries(success, fail);
function success(entries) {
var i;
for (i=0; i<entries.length; i++) {
console.log(entries[i].name);
}
}
function fail(error) {
console.log(error.code);
}
window.requestFileSystem(window.PERSISTENT, 0, initFS, error);
function initFS(fs) {
fs.root.getFile(„log.txt', {}, win, error);
}
function win(fileEntry) {
fileEntry.file(read, error);
}
function read(file) {
var reader = new FileReader();
reader.onloadend = function(e) {
console.log(this.result);
};
reader.readAsText(file);
}
function error(err) { console.log(err);}
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