计算

data(){
	return {
		fileSizeString:''
	}
},

//methods
formatSize() {  
  	let that = this;  
  	plus.cache.calculate(function(size) {  
 	 let sizeCache = parseInt(size);  
 	 if (sizeCache == 0) {  
    	 that.fileSizeString = "0B";  
  	} else if (sizeCache < 1024) {  
   	  that.fileSizeString = sizeCache + "B";  
  	} else if (sizeCache < 1048576) {  
   	  that.fileSizeString = (sizeCache / 1024).toFixed(2) + "KB";  
 	 } else if (sizeCache < 1073741824) {  
    	 that.fileSizeString = (sizeCache / 1048576).toFixed(2) + "MB";  
 	 } else {  
    	 that.fileSizeString = (sizeCache / 1073741824).toFixed(2) + "GB";  
 	 }  
	});  
}

清除

 clearCache() {  
      let that = this;  
      let os = plus.os.name;  
       if (os == 'Android') {  
           let main = plus.android.runtimeMainActivity();  
           let sdRoot = main.getCacheDir();  
           let files = plus.android.invoke(sdRoot, "listFiles");  
           let len = files.length;  
           for (let i = 0; i < len; i++) {  
           		let filePath = '' + files[i]; // 没有找到合适的方法获取路径，这样写可以转成文件路径  
                    plus.io.resolveLocalFileSystemURL(filePath, function(entry) {  
                            if (entry.isDirectory) {  
                                entry.removeRecursively(function(entry) { //递归删除其下的所有文件及子目录  
                                    uni.showToast({  
                                        title: '缓存清理完成',  
                                        duration: 2000  
                                    });  
                                    that.formatSize(); // 重新计算缓存  
                                }, function(e) {  
                                    console.log(e.message)  
                                });  
                            } else {  
                                entry.remove();  
                            }  
                        }, function(e) {  
                            console.log('文件路径读取失败')  
                        });  
                    }  
                } else { // ios  
                    plus.cache.clear(function() {  
                        uni.showToast({  
                            title: '缓存清理完成',  
                            duration: 2000  
                        });  
                        that.formatSize();  
                    });  
                }  
            }